Cooperative MIMO

ABSTRACT

In a multiuser (MU) multiple antenna system (MAS), a central processing unit is communicatively coupled to multiple distributed wireless terminals (WTs) via a network. The central processing unit processes channel measurements indicative of channel conditions between the multiple distributed WTs and a plurality of user devices and selects a plurality of WTs from the multiple distributed WTs to enhance channel space diversity within the MU-MAS. The central processing unit calculates (Multiple Input, Multiple Output) MIMO weights from the channel measurements for precoding a plurality of data streams that are transmitted concurrently from the plurality of WTs to the plurality of users, wherein the MIMO weights provide for a plurality of independent MIMO channels.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/168,466, filed Jan. 30, 2014, which is a Continuation-in-Part of U.S.patent application Ser. No. 11/187,107, filed on Jul. 22, 2005, now U.S.Pat. No. 8,670,390, which claims priority to Provisional Appl. No.60/598,187, filed Aug. 2, 2004, all of which are hereby incorporated byreference in their entireties and all of which this application claimspriority under at least 35 U.S.C. 120 and/or any other applicableprovision in Title 35 of the United States Code. U.S. patent applicationSer. No. 09/718,851, filed on Nov. 22, 2000 is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION I. Field of the Invention

The present invention relates generally to antenna-array processing andad-hoc networking, and particularly to providing cooperative signalprocessing between a plurality of wireless terminal devices, such as toimprove network access.

II. Description of the Related Art

Wireless data service is an emerging market with high growth potential.However, market growth requires higher bandwidth and better coveragethan cellular technologies can provide. Furthermore, state-of-the-artwireless network technologies are mainly focused on the server side,rather than using mobile wireless terminals to extend the networkinfrastructure.

A peer-to-peer mode of communication is expected to offer distinctperformance benefits over the conventional cellular model, includingbetter spatial-reuse characteristics, lower energy consumption, andextended coverage areas. The key advantage of the peer-to-peer networkmodel is the increase in spatial reuse due to its short-rangetransmissions. Although peer-to-peer networking shows some promise,there are significant drawbacks that prevent conventional peer-to-peernetworks from being a technically and commercially viable solution.

Recent analyses of multi-hop networks compared to cellular networks haveindicated that the spatial reuse improvement in the peer-to-peer networkmodel does not translate into greater throughput. Rather, the throughputis lower than that observed in the cellular network model. Thisobservation is explained in three parts:

Multi-hop Routes: Although the spatial reuse is increased, since a flowtraverses multiple hops in the peer-to-peer network model, theend-to-end throughput of a flow, while directly proportional to thespatial reuse, is also inversely proportional to the hop-length.Moreover, since the expected hop-length in a dense network is of theorder of O(√n), a tighter bound on the expected per-flow throughput isO(1/√n). While this bound is still higher than that of the densecellular network model (O(1/n)), the following two reasons degrade theperformance even more.

Base-Station Bottleneck: The degree of spatial reuse and expectedper-flow throughput of the peer-to-peer network model is valid for anetwork where all flows have destinations within the same cell. In thiscase, the base station is the destination for all flows (e.g., it is thedestination of the wireless path). Thus, any increase in spatial reusecannot be fully realized as the channel around the base-station becomesa bottleneck and has to be shared by all the flows in the network. Notethat this is not an artifact of the single-channel model. As long as theresources around the base-station are shared by all the flows in thenetwork (irrespective of the number of channels), the performance of theflows will be limited to that of the cellular network model.

Protocol Inefficiencies: The protocols used in the cellular networkmodel are both simple and centralized, with the base station performingmost of the coordination. Cellular protocols operate over a single hop,leading to very minimal performance degradation because of protocolinefficiencies. However, in the peer-to-peer network model, theprotocols (such as IEEE 802.11 and DSR) are distributed, and theyoperate over multiple hops. The multi-hop path results in more variationin latency, losses, and throughput for TCP. These inefficiencies (whicharise because of the distributed operation of the medium access androuting layers) and the multi-hop operation at the transport layertranslate into a further degraded performance.

Similarly, antenna-array processing has demonstrated impressiveimprovements in coverage and spatial reuse. Array-processing systemstypically employ multiple antennas at base stations to focus transmittedand received radio energy and thereby improve signal quality. Incellular communications, improvements in signal quality lead tosystem-wide benefits with respect to coverage, service quality and,ultimately, the economics of cellular service. Furthermore, theimplementation of antenna arrays at both ends of a communication linkcan greatly increase the capacity and performance benefits via MultipleInput Multiple Output (MIMO) processing. However, power, cost, and sizeconstraints typically make the implementation of antenna arrays onmobile wireless terminals, such as handsets or PDAs, impractical.

In cooperative diversity, each wireless terminal is assigned anorthogonal signal space relative to the other terminals for transmissionand/or reception. In particular, both multiplexing and multiple accessin cooperative diversity are orthogonal. In antenna-array processing,either or both multiplexing and multiple access are non-orthogonal.Specifically, some form of interference cancellation is required toseparate signals in an array-processing system because transmittedand/or received information occupies the same signal space.

Applications and embodiments of the present invention relate to ad-hocnetworking and antenna-array processing. Embodiments of the inventionmay address general and/or specific needs that are not adequatelyserviced by the prior art, including (but not limited to) improvingnetwork access (e.g., enhancing range, coverage, throughput,connectivity, and/or reliability). Applications of certain embodimentsof the invention may include tactical, emergency response, and consumerwireless communications. Due to the breadth and scope of the presentinvention, embodiments of the invention may be provided for achieving alarge number of objectives and applications, which are too numerous tolist herein. Therefore, only some of the objects and advantages ofspecific embodiments of the present invention are discussed in theSummary and in the Preferred Embodiments.

SUMMARY OF THE INVENTION

Some of the exemplary embodiments of the present invention aresummarized as follows. Embodiments of the invention include beam-formingsystems configured to enable spatially separated wireless terminals(WTs) to perform beam-forming operations in a wireless wide area network(WWAN). A wireless local area network (WLAN) couples together the WTs,which may be configured to share WWAN data, access, and controlinformation. A beam-forming system may comprise the WTs, which functionas elements of an antenna array. WWAN network access functions (such asmonitoring control channels and exchanging control messages with theWWAN) may be provided in a centralized or a distributed manner withrespect to the WTs.

Embodiments of the invention also include systems and methods configuredfor allocating network resources among the WTs, load balancing,distributed computing, antenna-switching diversity, WWAN diversity,interference mitigation, hand off, power control, authentication,session management, ad-hoc network control, error correction coding, andinterference mitigation. Other embodiments and variations thereof aredescribed in the Description of Preferred Embodiments.

In one embodiment, a computer program comprises a beam-forming weightcalculation source code segment adapted to calculate at least one set ofbeam-forming weights for signaling between at least one group of WTs andat least one WWAN, and a WLAN information-distribution source codesegment adapted to distribute at least one of a set of signals betweenthe at least one group of WTs, the set of signals including a pluralityof received WWAN signals, a plurality of WWAN transmission data, and theat least one set of beam-forming weights.

In another embodiment. a computer program comprises a beam-formingweight source code segment adapted to calculate at least one set ofbeam-forming weights for signaling between at least one group of WTs andat least one WWAN, and a MIMO combining source code segment adapted tocombine a plurality of weighted received WWAN signals, at least one ofthe beam-forming weight source code segment and the MIMO combiningsource code segment including WLAN information-distribution source codeadapted to distribute at least one of a set of signals between the atleast one group of wireless terminals, the set of signals including aplurality of received WWAN signals, a plurality of WWAN transmissiondata, at least one channel estimate, and the at least one set ofbeam-forming weights.

A receiver embodiment of the invention comprises a plurality of WWANinterfaces, wherein each WWAN interface is adapted to receive at leastone transmitted WWAN signal; a plurality of baseband processors whereineach baseband processor is coupled to at least one WWAN interface in theplurality of WWAN interfaces, the plurality of baseband processorsadapted to generate a plurality of WWAN baseband signals; at least oneWLAN coupled to the plurality of baseband processors; and at least oneMIMO combiner adapted to receive at least one WWAN baseband signal fromthe WLAN, the at least one MIMO combiner adapted to perform MIMOcombining of a plurality of WWAN baseband signals.

A transmitter embodiment of the invention comprises a plurality of WWANinterfaces wherein each WWAN interface is adapted to transmit at leastone WWAN signal; at least one data source adapted to generate at leastone data signal for transmission into at least one WWAN; at least oneWLAN adapted to couple the at least one data signal to the plurality ofWWAN interfaces for generating a plurality of WWAN data signals; and atleast one MIMO processor adapted to generate a plurality of complexweights for weighting the plurality of WWAN data signals.

A wireless terminal according to one aspect of the invention comprisesat least one WWAN interface; at least one WLAN interface; and at leastone cooperative beam-forming system coupled between the WWAN interfaceand the WLAN interface and adapted to perform beamforming withinformation received from the WLAN interface.

Receivers and cancellation systems described herein may be employed insubscriber-side devices (e.g., cellular handsets, wireless modems, andconsumer premises equipment) and/or server-side devices (e.g., cellularbase stations, wireless access points, wireless routers, wirelessrelays, and repeaters). Chipsets for subscriber-side and/or server-sidedevices may be configured to perform at least some of the receiverand/or cancellation functionality of the embodiments described herein.

Additional embodiments, objects, and advantages are described andinferred from the following detailed descriptions and figures. Althoughparticular embodiments are described herein, many variations andpermutations of these embodiments fall within the scope and spirit ofthe invention. Although some benefits and advantages of the preferredembodiments are mentioned, the scope of the invention is not intended tobe limited to particular benefits, uses, or objectives. Rather,embodiments of the invention are intended to be broadly applicable todifferent wireless technologies, system configurations, networks, andtransmission protocols, some of which are illustrated by way of examplein the figures and in the following description of the preferredembodiments. The detailed description and drawings are merelyillustrative of the invention rather than limiting, the scope of theinvention being defined by the appended claims and equivalents thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an application of various embodiments of theinvention to a cellular network.

FIG. 1B illustrates an embodiment of the invention in which transmittedand/or received data between a WLAN group and a WWAN terminal occupiesparallel, redundant channels c_(n).

FIG. 1C illustrates an embodiment of the invention in which a WLAN groupcomprising a plurality of Wireless Terminals (WTs) is adapted tocommunicate with at least one WWAN node.

FIG. 1D illustrates an embodiment of the invention in whichcommunications between a WWAN node and a plurality of WTs arecharacterized by different, yet complementary, code spaces c₁, c₂, andc₃.

FIG. 1E illustrates an embodiment of the invention in which a first WLANgroup is adapted to communicate with a second WLAN group via at leastone WWAN channel or network.

FIG. 1F shows an embodiment of the invention wherein a WLAN groupincludes a plurality of WWAN-active WTs and at least one WWAN-inactiveWT.

FIG. 1G illustrates a cooperative beam-forming embodiment of theinvention that functions in the presence of a desired WWAN terminal anda jamming source.

FIG. 1H illustrates a cooperative beam-forming embodiment of theinvention that functions in the presence of a plurality of desired WWANterminals.

FIG. 1I illustrates an embodiment of the invention adapted to provide aplurality of WTs in a WLAN group with access to a plurality of WWANservices.

FIG. 1J illustrates an embodiment of the invention in which a WLAN groupincludes at least one WWAN terminal.

FIG. 2A illustrates a functional receiver embodiment of the inventionthat may be realized in both method and apparatus embodiments.

FIG. 2B illustrates a functional receiver embodiment of the inventionthat may be realized in both method and apparatus embodiments.

FIG. 3A illustrates an embodiment of the invention in which a WLANcontroller for a WLAN group allocates processing resources based onWWAN-link performance.

FIG. 3B illustrates an alternative embodiment of the invention in whicha WLAN controller for a WLAN group allocates processing resources basedon WWAN-link performance.

FIG. 4A illustrates a MIMO receiver embodiment of the invention.

FIG. 4B illustrates a functional embodiment of the invention in whichMIMO processing operations are distributed over two or more WTs.

FIG. 4C illustrates a functional embodiment of the invention fortransmission and reception of WWAN signals in a distributed network ofWTs.

FIG. 4D illustrates a functional embodiment of the invention adapted toperform cooperative beamforming.

FIG. 5A illustrates a receiver embodiment of the invention that may beimplemented by hardware and/or software.

FIG. 5B illustrates an alternative receiver embodiment of the invention.

FIG. 6A illustrates functional and apparatus embodiments of the presentinvention pertaining to one or more WTs coupled to at least one WWAN andat least one WLAN.

FIG. 6B illustrates a preferred embodiment of the invention that may beemployed as either or both apparatus and functional embodiments of oneor more WTs.

FIG. 7A illustrates a functional embodiment of the invention related tocalculating MIMO weights in a cooperative-beamforming network.

FIG. 7B illustrates a functional embodiment of the invention adapted tocalculate transmitted data symbols received by a cooperative-beamformingnetwork.

FIG. 8A illustrates a preferred transmitter embodiment of the invention.

FIG. 8B illustrates a preferred receiver embodiment of the invention.

FIG. 8C illustrates an embodiment of the invention in which a pluralityof WTs is adapted to perform time-domain processing.

FIG. 9A illustrates an optional transmission embodiment of the presentinvention.

FIG. 9B illustrates a functional flow chart that pertains to transmitterapparatus and method embodiments of the invention.

FIG. 10A illustrates software components of a transmission embodiment ofthe invention residing on a computer-readable memory.

FIG. 10B illustrates software components of a receiver embodiment of theinvention residing on a computer-readable memory.

FIG. 11 shows a WWAN comprising a WWAN access point (e.g., a basestation) and a local group comprising a plurality of wireless terminalscommunicatively coupled together via a WLAN. A network-managementoperator is configured to handle WWAN-control operations within thelocal group.

DESCRIPTION OF PREFERRED EMBODIMENTS

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the exemplary embodiments are not intended tolimit the invention to the particular forms disclosed. Instead, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims.

FIG. 1A illustrates how some embodiments of the invention may beemployed in a cellular network. Each wireless terminal (WT) of aplurality of WTs 101-103 is in radio contact with at least one wirelesswide area network (WWAN) terminal, which may also be referred to as aWWAN node, such as cellular base station 119. The cellular base station119 may include one or more antennas (e.g., an antenna array). WWANsignals transmitted between the base station 119 and the WTs 101-103propagate through a WWAN channel 99, which is typically characterized byAWGN, multipath effects, and may include external interference.

The WTs 101-103 represent a wireless local area network (WLAN) group 110(or local group) if they are currently connected or are capable of beingconnected via a WLAN 109. Accordingly, the WTs may be adapted to connectto at least one WWAN and to at least one WLAN. The WLAN group 110 mayconsist of two or more WTs in close enough proximity to each other tomaintain WLAN communications. A given WWAN may include one or more WLANgroups, such as WLAN group 110.

In an exemplary embodiment of the present invention, the WTs 101-103 maybe configured to transmit data d_(t)(n) over a WWAN channel to the basestation 119. The WTs 101-103 may also be configured to receive datad_(r)(n) on a WWAN channel from the base station 119. The received datad_(r)(n) is shared by the WTs 101-103 via the WLAN 109. Similarly, thetransmitted data d_(t)(n) may be distributed to the WTs 101-103 via theWLAN 109. The WLAN 109 typically comprises the wireless-communicationresource between the WTs 101-103 and the associated physical-layerinterface hardware. The WLAN 109 is differentiated from a WWAN by itsrelatively shorter range. For example, a Bluetooth or UWB systemfunctioning within an IEEE 802.11 network would be referred to as aWLAN, whereas the 802.11 network would be referred to as a WWAN. A WLANmay operate in a different frequency band than the WWAN. Alternatively,other orthogonalizing techniques may be employed for separating WLAN andWWAN signals from each other. WLANs and WWANs, as defined herein, mayemploy any type of free-space transmissions, including, but not limitedto, ultra-low frequency, RF, microwave, infrared, optical, and acoustictransmissions. WLANs and WWANs may employ any type of transmissionmodality, including, but not limited to, wideband, UWB, spread-spectrum,multi-band, narrowband, or dynamic-spectrum communications.

The WLAN 109 may also comprise the WLAN network-control functionalitycommonly associated with a WLAN, and the WWAN-access controlfunctionality required to distribute necessary WWAN-access parameters(e.g., node addresses, multiple-access codes, channel assignments,authentication codes, etc.) between active WTs 101-103. The distributionof WWAN-access parameters between multiple WTs 101-103 enables each WT101-103 to be responsive to transmissions intended for a particular WTin the local group and/or it enables a plurality of WTs 101-103 tofunction as a single WT when transmitting signals into the WWAN channel99.

Particular embodiments of the invention provide for adapting either orboth the transmitted data d_(t)(n) and the received data d_(r)(n) inorder to perform beamforming. Specifically, the group of WTs 110 may beadapted to perform antenna-array processing by linking the individualWTs together via WLAN links 109 and employing appropriate antenna-arrayprocessing on the transmitted and/or the received data, d_(t)(n) andd_(r)(n), respectively.

Ad-hoc wireless networks (e.g., multi-hop and peer-to-peer networks) mayemploy intermediate relay nodes to convey transmissions from a source toa destination. Relays reduce the transmission power requirements forsending information over a given distance. This indirectly increases thespatial-reuse factor, thus enhancing system-wide bandwidth efficiency.For this reason, ad-hoc wireless networking works particularly well withunlicensed spectrum, which is characterized by restrictive powerlimitations and high path loss compared to cellular bands. Similarly,for certain embodiments of the invention, it may be preferable to employhigh-loss (e.g., high-frequency) channels for the WLAN connections 109.

The capacity of wireless ad-hoc networks is constrained by interferencecaused by the neighboring nodes, such as shown in P. Gupta and P. R.Kumar, “The Capacity of Wireless Networks,” IEEE Trans. Info. Theory,vol. IT-46, no. 2, March 2000, pp. 388-404 and in A. Agarwal and P. R.Kumar, “Improved capacity bounds for wireless networks.” WirelessCommunications and Mobile Computing, vol. 4, pp. 251-261, 2004, both ofwhich are incorporated by reference herein. Using directional antennas(such as antenna arrays) reduces the interference area caused by eachnode, which increases the capacity of the network. However, the use ofdirectional antennas and antenna arrays on the WTs 101-103 is often notfeasible, especially when there are size constraints, powerrestrictions, cost constraints, and/or mobility needs. Thus, someembodiments of the present invention may provide for enabling WTs toform groups that cooperate in network-access functions. This provideseach member of a given WLAN group with greater network access, as wellas other benefits.

Antenna-array processing is generally categorized as multiple-input,single-output (MISO), single-input, multiple-output (SIMO) or multipleinput, multiple output (MIMO). Array processing often employs beamforming in at least one predetermined signal space or signal sub-space.For example, phased-array processing involves coherent beam-forming ofat least one transmitted signal frequency. Sub-space processing oftenemploys some form of baseband interference cancellation or multi-userdetection. Other variations of phased-array and sub-space processingalso exist and may be implemented in embodiments of the presentinvention.

Sub-space processing is commonly employed via space-time processing(e.g., Rake receivers are employed in a frequency-selective channel)and/or space-frequency processing (e.g., frequency-domain processing isemployed to provide for multiple flat-fading channels). Similarly,sub-space processing may employ other diversity parameters andcombinations thereof, including (but not limited to) polarizationprocessing and code-space processing.

MIMO systems have been shown to significantly increase the bandwidthefficiency while retaining the same transmit power budget andbit-error-rate (BER) performance relative to a single input, singleoutput (SISO) system. Similarly, for a given throughput requirement,MIMO systems require less transmission power than SISO systems. MIMOtechnology is useful for enabling exceptionally high bandwidthefficiency. However, many spatial-multiplexing techniques require richscattering. Increased path loss and poor scattering are major problemsfor MIMO systems operating above 2.4 GHz. For these reasons, lower(e.g., cellular) frequencies are often preferred for MIMO applications.However, some MIMO benefits can also be achieved at higher frequencies.

FIG. 1B illustrates an embodiment of the present invention in whichtransmitted and/or received data between the WLAN group 110 and the WWANterminal 119 occupies parallel, redundant channels c_(n). This approachis distinct from typical cooperative-diversity implementations in whichWWAN data transmissions are conveyed over a plurality of orthogonalchannels. Rather, each of the WTs 101-103 transmits and/or receives on acommon channel c_(n). This enables many well-known types of arrayprocessing to be performed.

The WLAN group 110 may function as either or both a transmitting arrayand a receiving array. The signal received at an antenna array is anoisy superposition of the n transmitted signals:

${y(n)} = {{\sqrt{\frac{E_{s}}{M_{t}}}{{Hs}(n)}} + {v(n)}}$where {s(n)}_(n=0) ^(N-1) is a sequence of transmitted vectors, E_(s)corresponds to the transmit energy assuming that E_(sn)∥s_(n)∥=1 forn=1, . . . , M_(t), ν(n) represents AWGN with zero mean and variance,and H is an M_(r)×M_(t) matrix channel (where M_(r) is the number ofreceiver elements and M_(t) is the number of transmitter elements),which is assumed constant over N symbol periods. The nominal rank of arational matrix H is the order of the largest minor of H that is notidentically zero, such as shown in T. Kailath, Linear Systems,Prentice-Hall, Inc., 1980, (especially Sec. 6.5), which is incorporatedby reference.

Channel characterization involves finding a set of channel realizations(e.g., functions) that indicate channel quality with respect to someperformance metric (e.g., error probability or asymptotic criteria). Inthe MIMO channel, several variables contribute to the channel quality(and thus, to the optimization of channel quality), including the choiceof space-time codes, receiver-terminal selection, and receiveralgorithm(s) employed.

In one embodiment of the invention, a subset of WTs in a WLAN group maybe selected such as to provide optimal WWAN transmission and/orreception within at least one predetermined constraint, such as anoptimal or maximum number of active WWAN transceivers within the WLANgroup. Such predetermined constraints may be established to optimizesome combination of WWAN link performance and resource use within theWLAN group. In one embodiment, WTs experiencing the best WWAN channelconditions may be selected. Techniques employing antenna selection, suchas may be used for diversity processing with antenna arrays, may be usedin embodiments of the present invention. In one aspect of the invention,resource conservation may focus on WT battery power, MIMO processingcomplexity, and/or WLAN bandwidth.

Certain embodiments of the invention may distinguish between circuitpower (e.g., power used to perform signal processing) versustransmission power. Other embodiments of the invention may provideconsideration for the total battery power (e.g., processing power plustransmission power) budget, such as to provide power (e.g., batteryusage) load balancing between WTs. Thus, embodiments of the inventionmay optimize a balance of signaling parameters, including (but notlimited to) transmission power, channel-coding (and decoding)complexity, modulation, signal processing and the complexity associatedwith cooperative array processing parameters (e.g., number of activearray elements, number of channels, number of WTs employed to performsignal processing, number of WTs in a WLAN group, type ofarray-processing operations, etc.).

Any combination of various channel-characterization functions may beemployed as a measure of link performance. Example functions including,but not limited to, the following may be employed. Possible functionsinclude the average signal strength:

${P(H)} = {\frac{1}{N}{\sum\limits_{n = 0}^{N - 1}{H^{(n)}}_{F}^{2}}}$the average mutual information:

${\overset{\_}{I}(H)} = {\frac{1}{N}{\sum\limits_{n = 0}^{N - 1}{\log\;{\det\left( {I_{M_{r}} + {\frac{E_{s}}{N_{o}M_{t}}H^{(n)}H^{{(n)}H}}} \right)}}}}$and the normalized average mutual information:

${\overset{\_}{I}(H)} = {\frac{1}{N}{\sum\limits_{n = 0}^{N - 1}{\log\;{\det\left( {I_{M_{r}} + {\frac{E_{s}}{N_{o}}\frac{1}{\alpha}H^{(n)}H^{{(n)}H}}} \right)}}}}$

where

$\alpha = {\frac{1}{{NM}_{t}M_{r}}{\sum\limits_{n = 0}^{N - 1}{H^{(n)}}_{F}^{2}}}$is an estimate of the path loss.

Theoretical capacity in a MIMO channel is typically expressed as:C=log_(d) det[I _(M) _(r) +ρ/M _(t) HH*]where ρ is the average SNR.

A preferred embodiment of the invention may employ error-correctingcodes to add structured redundancy to the information bits. This can bedone to provide diversity, such as temporal diversity, spatialdiversity, and/or frequency diversity. Embodiments of the invention mayemploy spreading codes, which are well known in the art. In addition tocollaborative MIMO operations, the WTs may engage in collaborativedecoding. In particular, a WLAN group may be provided with functionalitythat directs the WTs to coordinate WWAN information exchange anddecoding via the WLAN.

In yet another embodiment of the invention, a WWAN terminal may beadapted to receive channel information (and/or even received data) fromWTs, perform array-processing (e.g., MIMO) computations, and then uploadthe resulting array-processing weights to the WTs. The WTs may simplyapply the weights to their transmitted and/or received WWAN signals, andperform any other related operations, such as combining.

FIG. 1C illustrates a WLAN group 110 comprising a plurality of WTs101-103 adapted to communicate with at least one WWAN node 119. A WWANchannel 99 expresses distortions, interference, and noise that affectWWAN transmissions between the WTs 101-103 and the WWAN node 119.Channel estimation characterizes propagation characteristics (e.g.,multipath, shadowing, path loss, noise, and interference) in the WWANchannel.

In one embodiment of the invention, a given WWAN transmission isseparated into spectral components (such as denoted by f₁, f₂, and f₃)by the WLAN group 110. For example, each of the WTs 101-103 may beadapted to receive predetermined spectral components f₁, f₂, and f₃ of agiven transmission intended for a particular WT. Alternatively, each ofthe WTs 101-103 may be adapted to transmit one or more associatedpredetermined spectral components to the WWAN node 119.

The selection of spectral components f₁, f₂, and f₃ and theirassociation with particular WTs 101-103 is typically performed tooptimize WWAN system performance relative to the current WWAN channel99. For example, since the frequency-dependent fading profile in ascattering-rich environment tends to be unique for each spatiallyseparated WT 101-103 channel, the spectral components f₁, f₂, and f₃ arepreferably selected to minimize the effects of deep fades and/orinterference. Spectral-component selection may be selected and/oradapted to optimize one or more WWAN link-performance metrics,including, but not limited to, SNR, BER, PER, and throughput.Spectral-component selection may be performed to achieve otherobjectives, such as to distribute processing loads across the WLAN group110.

The spectral components f₁, f₂, and f₃ may be characterized byoverlapping or non-overlapping frequency bands. Spectral components f₁,f₂, and f₃ may each include continuous or discontinuous (e.g., frequencyinterleaved) frequency-band components. Spectral components f₁, f₂, andf₃ may comprise similar or different bandwidths. Furthermore, thespectral components f₁, f₂, and f₃ may include gaps or notches, such asto notch out interference or deep fades. Accordingly, an aggregatesignal derived from combining the spectral components f₁, f₂, and f₃ mayinclude gaps or notches.

WWAN communication signals may include multicarrier (e.g., OFDM) orsingle-carrier signals. In the case of single-carrier signals, the WTs101-103 can be adapted to perform frequency-domain synthesis and/ordecomposition, such as described in published patent appl. nos.20040086027 and 20030147655, which are hereby incorporated by referencein their entireties.

FIG. 1D illustrates a similar communication-system embodiment to thatshown in FIG. 1C, except that the transmissions between the WWAN node119 and the WTs 101-103 are characterized by different, yetcomplementary, code spaces c₁, c₂, and c₃. In this case, the termcomplementary means that the coded transmissions corresponding to thecode spaces c₁, c₂, and c₃ can sum to produce at least one predeterminedWWAN coded data sequence. This may be a weighted sum due to the givenchannel conditions. A predetermined WWAN coded data sequence may employa code that would ordinarily (in view of the prior art) be employed inwhole. That is, it would not ordinarily be partitioned into sub-codes tobe transmitted by different transmitters or received by differentreceivers.

In one embodiment of the invention, the code spaces c₁, c₂, and c₃correspond to direct-sequence codes, such as may be used to provide forspreading and/or multiple access. A superposition of signals transmittedacross the code spaces c₁, c₂, and c₃ may provide at least onepredetermined WWAN coded data sequence received by at least one WWANnode 119. Similarly, a superposition of signals received by the WTs101-103 and mapped onto the code spaces c₁, c₂, and c₃ may provide atleast one predetermined WWAN coded data sequence that would ordinarily(in view of the prior art) be intended for a single WT. Preferredembodiments of the invention may provide for channel corrections (e.g.,pre-distortion and/or receiver-side channel compensation) by either orboth the WLAN group 110 and the WWAN node 119. Accordingly, the codespaces c₁, c₂, and c₃ may be adapted to account for channel conditions.

In another embodiment of the invention, the code spaces c₁, c₂, and c₃may correspond to direct-sequence codes having predetermined spectralcharacteristics. It is well known that different time-domain datasequences may be characterized by different spectral distributions.Accordingly, embodiments of the invention may provide for selectingcomplementary codes c₁, c₂, and c₃ having predetermined spectralcharacteristics with respect to WWAN channel conditions affecting thelinks between the WTs 101-103 and the WWAN node 119. Thus, the codes C₁,c₂, and c₃ may be selected according to the same criteria employed forselecting the spectral components f₁, f₂, and f₃.

FIG. 1E illustrates an embodiment of the invention in which a first WLANgroup 110 (such as comprising WTs 101-103 connected via WLAN 109) isadapted to communicate with a second WLAN group 120 (such as comprisingWTs 111-113 connected via WLAN 118) via WWAN channel 99. Applications ofthis embodiment may be directed toward peer-to-peer and multi-hopnetworks. Specifically, antenna-array processing (e.g., MIMO operations)may be performed by both WLAN groups 110 and 120. Each WLAN group (suchas WLAN groups 110 and 120) may function as a single node in an ad-hocnetwork, a peer-to-peer network, or a multi-hop network. For example,any communication addressed to (or routed through) a particular node(such as one of the WTs 101-103) may be advantageously processed by oneor more of the WTs 101-103 in the WLAN group 110. In one embodiment,each active WT 101-103 in the WLAN group 110 may be responsive tocommunications addressed to itself and to at least one other WT 101-103in the WLAN group 110.

The WLAN 109 may be used to inform individual WTs 101-103 which nodeaddress(es) (or multiple-access channel assignments) to be responsiveto. Similarly, the WLAN 109 may convey information to WTs 101-103 inorder to spoof node addresses and/or multiple-access information andotherwise help WTs 101-103 assume channelization information related toa particular WT identity prior to transmitting signals into the WWAN.Thus, the WLAN 109 can be used to assist in synchronizing WTinteractions with the WWAN. The functionality of providing for sharingWWAN-access information between WTs 101-103 may be coordinated andcontrolled with respect to cooperative-array (e.g., MIMO) processing.

FIG. 1F shows an embodiment of the invention wherein a WLAN group 110includes a plurality of WWAN-active WTs 101-103 and at least oneWWAN-inactive WT, such as WTs 104-106. The WWAN-active WTs 101-103 maybe configured to directly transmit and/or receive WWAN communicationsignals 129. WWAN-inactive WTs 104-106 are defined as WLAN-connectedterminals that do not directly communicate with the WWAN. Rather, theWWAN-inactive WTs 104-106 may be in a sleep or standby mode.

In a preferred embodiment of the invention, signals routed to and from aparticular WT 101-103 may be provided with beam-forming weights thatallow for phased-array and/or sub-space processing. Calculation of theweights may be facilitated via distributed computing (e.g., as aload-balancing measure) across a plurality of the WTs (101-106). Thisallows the WLAN group 110 to scale the effective throughput of the WWANlink and coordinate system throughput with local area load balancing. Inparticular, the efficiency of the WWAN link is proportional to thesmaller of the number of array elements at the WWAN terminal (not shown)and the number of WWAN-active transceiver antennas linked by the WLAN109. When an equal number N of antennas is employed on both sides of thelink, up to an N-fold increase in the link throughput is possible.Channel coding can be employed to exchange this increase for improvedprobability-of-error performance, increased range, and/or lowertransmission power.

Although the capacity of a MIMO channel increases with the number ofantennas employed at both ends of the link, the complexity of thetransmission and reception algorithms increases accordingly. Forexample, the sphere decoder has a typical complexity of O(M_(T) ⁶),where M_(T) is the number of transmitting antennas, and V-Blast has atypical complexity of O((M_(R)M_(T))³), where M_(R) and M_(T) arerespectively the number of receiving and transmitting antennas. However,the computational power increases only linearly with respect to thenumber of WTs (assuming each WT has identical processing capability).Thus, the aggregate processing power of the WTs may determine themaximum number of active antennas that a WLAN group 110 can support.

One solution to the disparity between required processing power and thenumber of WT processors in a given WLAN group 110 is to ensure that thetotal number of WTs exceeds the number of MIMO channels in the group110. This approach enables at least two significant processingadvantages:

-   -   1) The processing load may be spread over a larger number of        mobile-terminal processors, and    -   2) A form of antenna-switching diversity can be used to optimize        performance and throughput in the MIMO channel.        Antenna switching is a well-known technique that switches        between various antennas and selects ones having the best signal        outputs. This can be done to reduce correlation between        antennas, thereby improving MIMO performance. Antenna switching        is described in G. J. Foschini, M. J. Gans, “On limits of        wireless communication in a fading environment when using        multiple antennas,” Wireless Personal Communications, vol. 6,        no. 3, pp. 311-335, March 1998, which is incorporated by        reference. In some embodiments of the invention, WTs having the        most favorable WWAN channel characteristics may be selected to        improve MIMO performance without any increase in processing        complexity.

In some embodiments of the invention, one or more WWAN-inactive WTs104-106 may be employed for WLAN-based functions, such as (but notlimited to) WLAN network control, distributed-computing applications,and WWAN-interface control. For example, WLAN network control mayinclude any of the well-known network-control functions, such asterminal identification, authentication, error correction, routing,synchronization, multiple-access control, resource allocation, loadbalancing, power control, terminal-state management, hand-offs, etc.

The WLAN 109 may employ distributed computing across a plurality of theWTs. Distributed computing may be employed simply to achieve increasedprocessing power. Alternatively, distributed computing may include otherobjectives, such as balancing computational processing loads orbalancing power consumption across the WTs 101-106 in the WLAN group110. Computational loads on the WLAN group can potentially include anyWWAN-related computations, such as WWAN channel estimation, WWAN channelcompensation, diversity combining, WWAN channel coding/decoding, andcooperative array processing (e.g., MIMO weight calculation,interference cancellation, multi-user detection, matrix operations, andother smart antenna array processing operations).

WWAN-interface control may include distributing WWAN data and controlinformation between the WTs 101-106. In one exemplary embodiment of theinvention, at least one of the WTs 101-106 comprises a data source thatdistributes its data to at least one other WT 101-106 for transmissioninto the WWAN. In a similar embodiment of the invention, received WWANsignals intended for a particular WT 101-106 are received by a pluralityof WWAN-active WTs 101-103. The received WWAN signals may optionally beprocessed by one or more WTs 101-106 prior to being routed to theintended WT 101-106. Accordingly, WWAN channel-access information may berouted to a plurality of WWAN-active WTs 101-103 such that they functiontogether as a single WT 101-106.

The determination of which WTs 101-106 are active is typically performedby decision processing within the WLAN group 110 that determines whichWTs 101-106 have the highest quality WWAN channel(s). The number ofWWAN-active WTs (such as WTs 101-103) may be determined by one or morefactors, including WT channel quality, array-processing complexity,available computational resources within the WLAN group 110, loadbalancing, and information-bandwidth requirements. In an alternativeembodiment of the invention, the WWAN assigns cooperative channel-accessinformation to the WTs 101-103 and may optionally determine which WTs101-106 are active.

Some embodiments of the invention may take into consideration not onlythe MIMO complexity at the WTs, but also the added complexity associatedwith distributing the computational loads over WTs in a given WLANgroup. Both MIMO and distributed computing overheads can becharacterized as a function of the number of WTs in a WLAN group.Furthermore, the information bandwidth of a given WLAN channel limitsthe rate of information exchange between WTs. Accordingly, local channelconditions within the WLAN may affect throughput and range, and thuslimit the number of WTs within the WLAN group. Either the WLAN capacityor the computational capability of each WT may set a practical limit onthe number of WTs in a WLAN group and the overall frequency-reusefactor.

Another important factor that can impact the WLAN group size is thechannel rate-of-change, which may be due to motion of the WTs and/orother objects in the WWAN environment. In particular, rapidly changingchannel conditions may necessitate frequent updates to the MIMOcomputations, thus increasing the computational load on WLAN group andpotentially increasing the required data transfer across the WLAN.Similarly, local channel conditions may dictate the flow of data ifdistributed computing is employed.

MIMO systems experience substantial degradation in data transfer ratesin mobile channels. Time-varying multipath-fading profiles commonlyexperienced in a mobile wireless network exhibit deep fades that oftenexceed 30 dB. Commercial viability of some embodiments of the presentinvention requires the ability to tolerate a rapidly changing channel. Apromising approach to this problem is to employ diversity to reduce thechannel rate-of-change. In a wideband system, or equivalently, in asystem comprised of a number of narrowband subcarriers distributed(e.g., interleaved) over a wide frequency band, deep fades affect only aportion of the total channel bandwidth. Therefore, frequency and/orspatial diversity may be employed to reduce the likelihood of deep fadesin a multipath environment. Similarly, alternative forms of diversitymay be employed. In a mobile environment, this translates into reducingthe channel rate-of-change.

FIG. 1G illustrates a cooperative beam-forming embodiment of theinvention that functions in the presence of a desired WWAN terminal 119and an external interference source (or jammer) 118. WTs 101-103 in aWLAN group 110 may coordinate their received aggregate beam pattern(s)to null out a jamming signal 115. Array-processing operations performedon signals received from the WTs 101-103 may take the form ofphased-array processing, which minimizes the array's sensitivity tosignals arriving from one or more angles. Alternatively, arrayprocessing may employ baseband (or intermediate-frequency) interferencecancellation. Similarly, beam-forming operations may be employed tocancel emissions transmitted toward one or more terminals (such asjammer 118).

FIG. 1H illustrates a cooperative beam-forming embodiment of theinvention configured to function in the presence of a plurality ofdesired WWAN terminals 119 and 127. In one embodiment of the invention,the WWAN terminals 119 and 127 may be common to a particular WWAN, andthe configuration illustrated in FIG. 1H may include a soft hand-off inwhich redundant transmissions are transmitted between the WLAN group 110and the WWAN terminals 119 and 127. In this case, the WLAN group may bedistributed geographically over a plurality of WWAN sectors or cells. Inone aspect of the invention, the WLAN group 110 may adapt itsconnectivity with the WWAN to transition to the cell or sector offeringthe optimal aggregate WWAN channel quality. Accordingly, the WLAN groupmay adapt its selection of WWAN-active WTs in response to a hand off.

In another embodiment of the invention, the WLAN group 110 may employ afirst WWAN connection (such as illustrated by a connection between WTs101 and 102, and WWAN terminal 119) and a second WWAN connection (suchas illustrated by a connection between WT 103 and WWAN terminal 127) totransmit and/or receive one or more data streams. The WLAN group 110 mayemploy a plurality of WWAN user channels in a given WWAN. Similarly, theWLAN group 110 may employ connections to a plurality of different WWANs.

FIG. 1I illustrates an embodiment of the invention that provides aplurality of WTs 101-106 in a WLAN group 110 with access to a pluralityof WWAN services (i.e., WWANs). For example, WT 101 is provided with acommunication link with an IEEE 802.16 access-point terminal 116 in anIEEE 802.16 network, WT 102 maintains access capabilities to a3G-cellular terminal 119, and WT 103 has connectivity to an IEEE 802.11access point 117. WLAN connectivity 109 is adapted to enable any of theWTs 101-106 in the WLAN group 110 to access any of the plurality of WWAN(802.16, 3G, and 802.11) services.

The WLAN 109 may include a WWAN-access controller (not shown), which maytake the form of WLAN-control software residing on a physical device,such as one or more WTs 101-106. Connectivity of the WTs 101-106 to theavailable WWAN services may be performed with respect to a combinationof technical rules and business rules. For example, WWAN access istypically managed using technical rules, such as network load balancing,power conservation, and minimizing computational processing loads.However, WWAN access can also be influenced by business rules, such asenabling a predetermined cost/service ratio for individual WTs 101-106.For example, the WWAN-access controller (not shown) can anticipate theeconomic cost of particular WWAN services to the user, as well as usercommunication needs, when assigning WWAN access to individual WTs101-106. Each WT 101-106 may provide the WWAN-access controller (notshown) with a cost tolerance, which can be updated relative to the typeof communication link desired. For example, high-priority communicationneeds (such as particular voice communications or bidding on an onlineauction) may include permissions to access more expensive WWANconnections in order to ensure better reliability.

The overall goal of WWAN access may be to achieve optimal connectivitywith minimum cost. Accordingly, WWAN-access algorithms may includeoptimization techniques, including stochastic search algorithms (likemulti-objective genetic algorithms). Multi-objective optimization arewell known in the art, such as described in E. Zitzler and L. Thiele,“Multiobjective evolutionary algorithms: A comparative case study andthe strength pareto approach,” IEEE Tran. on Evol. Comput., vol. 3, no.4, November 1999, pp. 257-271 and J. D. Schaffer, “Multiple objectiveoptimization with vector evaluated genetic algorithms,” Proceedings of1st International Conference on Genetic Algorithms, 1991, pp. 93-100,both of which are incorporated by reference.

A WWAN-access controller (not shown) preferably ensures an uninterruptedsession when transitioning from one WWAN to another. In particular, thetransition between different WWANs should be invisible to the user. Thisrequires that the WWAN-access controller (not shown) be adapted to storeuser state information (e.g., save browser pages or buffer multimediadata streams). Furthermore, back-end systems may preferably be employedto manage cooperative WWAN access in order to consolidate differentWWAN-access charges into a single bill for the user.

In FIG. 1J, a plurality of WTs 101-106 in a WLAN group 110 includes atleast one WWAN terminal 106. The WTs 101-105 may contribute beam-formingcapabilities to the WWAN terminal 106, such as to increase range,increase spatial reuse, reduce transmission power, and/or achieve any ofother various beamforming objectives.

In one embodiment of the invention the WTs 101-105 function as lens forWWAN signals transmitted and received by the WWAN terminal 106. Forexample, the WTs 101-106 may collect received WWAN signals and thenfocus retransmitted WWAN signals at the WWAN terminal 106. Similarly,the WTs 101-105 may assist in the transmission of WWAN signals from theWWAN terminal 106 to one or more remote sources. In essence, the WTs101-105 may function like a radio relay, but with directionality andfocusing capabilities. In this embodiment, the WLAN connectivity of WTs101-105 with the WWAN terminal 106 may not be necessary.

In another embodiment of the invention, one or more of the WTs 101-106,such as WWAN terminal 106, may be adapted to process the majority (orentirety) of necessary beam-forming computations. In this case, WT 106is designated as a computer-processing terminal. The computer-processingterminal 106 is adapted to include specific computational resources forprocessing WWAN signals received by other WTs (such as WTs 101-103),which are then relayed via the WLAN 109 to the computer-processingterminal 106. Similarly, the computer-processing terminal 106 may beadapted to perform signal-processing operations associated with WWANtransmission. Computational operations associated with other WWANsignal-processing operations (e.g., coding, decoding, channelestimation, network-access control, etc.) may be provided by thecomputer-processing terminal 106.

FIG. 2A illustrates a functional embodiment of the invention that may berealized in both method and apparatus embodiments. A plurality M of WWANInterfaces 1101.1-1101.M is provided for coupling WWAN signals to and/orfrom at least one WWAN. In one functional embodiment, WWAN Interfaces1101.1-1101.M may include WWAN transceivers adapted to convert receivedWWAN signals into received baseband signals. A plurality of WWANbaseband processors 1102.1-1102.M are optionally provided for performingbaseband processing (such as, but not limited to, channel compensation,A/D conversion, frequency conversion, filtering, and demultiplexing) onthe received baseband signals. Alternatively, the function of the WWANbaseband processors 1102.1-1102.M may be performed by the WWANInterfaces 1101.1-1101.M.

Baseband outputs from the WWAN baseband processors 1102.1-1102.M arecoupled into a plurality of array processors, such as MIMO combiners1103.1-1103.M. In a MIMO channel, the received WWAN signals (and thus,the baseband outputs) are characterized by a plurality of overlapping(i.e., interfering) signals. Although MIMO combiners 1103.1-1103.M areshown, any type of array processor may be employed. The number of arrayprocessors may be less than, equal to, or greater than the number M ofWWAN Interfaces 1101.1-1101.M. Baseband outputs may also be coupled intoa WLAN 1105, which is coupled to the plurality of MIMO combiners1103.1-1103.M. Each MIMO combiner 1103.1-1103.M may be adapted toreceive baseband outputs from two or more baseband processors1102.1-1102.M wherein at least one of those baseband outputs is coupledto the MIMO combiner 1103.1-1103.M via the WLAN 1105.

A particular m^(th) MIMO combiner 1103.m need not process data from acorresponding (m^(th)) WWAN Interface 1101.m. Rather, the m^(th) MIMOcombiner 1103.m may process baseband signal outputs from a plurality ofWWAN Interfaces 1101.p {p=1, . . . , M, where p≠m}.

The WLAN 1105 comprises at least one WLAN channel between at least onebaseband output (e.g., baseband processor 1102.1-1102.M outputs) and atleast one array processor, such as the MIMO combiners 1103.1-1103.M. TheWLAN 1105 may include WLAN interfaces (not shown) and associatedWLAN-control hardware and/or software (not shown).

The MIMO combiners 1103.1-1103.M may be adapted to separate theoverlapping signals and output at least one desired transmissiontherefrom. Outputs of the MIMO combiners 1103.1-1103.M are optionallyprocessed by secondary data processors 1104.1-1104.M, which may providecoupling into the WLAN 1105. The secondary data processors 1104.1-1104.Mmay be adapted to perform demodulation, error-correction decoding, dataformatting, and/or other related baseband-processing functions.

In some embodiments of the invention, MIMO combiner 1103.1-1103.Moutputs may be coupled via the WLAN 1105 to other MIMO combiners1103.1-1103.M and/or secondary data processors 1104.1-1104.M. Forexample, embodiments of the invention may employ an iterativecancellation process, such as successive interference cancellation(which is well-known in the art), involving the use of strongest-signalestimates, and then next-strongest-signal estimates to cancel knowninterference in weaker signals. Alternatively, embodiments may employparallel cancellation.

FIG. 2B illustrates an embodiment of the invention including a pluralityM of WTs 1109.1-1109.M, each comprising a corresponding combination of aWWAN Interface 1101.1-1101.M, an optional WWAN baseband processor1102.1-1102.M, a combiner (such as a MIMO combiner 1103.1-1103.M), and asecondary data processor 1104.1-1104.M. The WTs 1109.1-1109.M arecoupled together by a WLAN 1105, which is configured to convey databetween the WTs 1109.1-1109.M in order to enable cooperativeantenna-array processing.

A WT, such as any of the WTs 1109.1-1109.M, includes any system ordevice provided with communicative connectivity means to a WLAN 1105.Two or more WTs 1109.1-1109.M are preferably provided with WWANinterfaces, such as WWAN Interface 1101.1-1101.M. A plurality of WTs1109.1-1109.M may share at least one WLAN 1105. In one embodiment of theinvention, individual WTs 1109.1-1109.M may share the same WWAN service.This enables the WLAN group 110 to perform either or both transmitbeam-forming and receive beam-forming (i.e., combining) operations.

In another embodiment of the invention, WTs 1109.1-1109.M may haveconnections to different WWANs and/or WWAN services. This enables theWLAN group 110 to achieve WWAN-service diversity. One or more WTs1109.1-1109.M may optionally be capable of accessing multiple WWANservices. For example, many cellular handsets are provided withmulti-mode capabilities, which give them the ability to access multipleWWANs. Some of the WTs 1109.1-1109.M may have no WWAN service. Forexample, one or more WTs 1109.1-1109.M may be out of range, in a WWANdead spot, in an inactive WWAN state, or configured only to communicatevia the WLAN 1105. WTs 1109.1-1109.M include, but are not limited to,cell phones, radio handsets, pagers, PDAs, wireless sensors, RFIDdevices, vehicle radio communication devices, laptop computers withwireless modems, wireless network access points, wireless routers,wireless switches, radio repeaters, transponders, and devices adapted toinclude satellite modems.

A WLAN group 110 may be adapted to perform any of various types andcombinations of diversity and MIMO beam-forming. Three commonly usedlinear diversity-combining techniques include switched (or selection)combining, maximal ration combining (MRC), and equal gain combining(EGC). Other combining techniques may be employed. The impact of usingdiversity may be expressed by a probability distribution p(γ) of the SNRγ at the output of a combining network. For switched diversity, whereinthe combiner switches to the diversity branches (e.g., WTs) having thestrongest signal, p(γ) is given by:

${p(\gamma)} = {\frac{L}{\Gamma}{e^{{- \gamma}/\Gamma}\left\lbrack {1 - e^{{- \gamma}/\Gamma}} \right\rbrack}^{L - 1}}$where Γ is the average SNR for each diversity branch and L is the numberof diversity branches. MRC weights branches (e.g., WT signals receivedfrom the WWAN) having better SNR more heavily (i.e., withgreater-magnitude weights) than branches having poorer SNR. The p(γ) forMRC is given by:

${p(\gamma)} = \frac{\gamma^{l - 1}e^{{- \gamma}/\Gamma}}{{\Gamma^{L}\left( {l - 1} \right)}!}$For EGC, p(γ) is given by:

${p(\gamma)} = {\frac{L}{a\;\Gamma}{e^{{{- \gamma}/a}\;\Gamma}\left\lbrack {1 - e^{{{- \gamma}/a}\;\Gamma}} \right\rbrack}^{L - 1}}$where a=√{square root over (L/1.25)} for L≥2, and 1 otherwise.These diversity techniques provide the greatest improvements when thebranches are uncorrelated.

Adaptive arrays (or smart antennas) may include antenna systems thatautomatically adjust to achieve some predetermined performancecriterion, such as maximizing the signal to interference (S/I) ratio,SINR, or link margin. Adaptive antenna techniques include switched beam,beam steering, and optimum combining (e.g., a linear spatial filteringapproach that employs adaptation to closely match an output signal witha reference signal). A filtering process typically suppresses anyartifacts that are not part of the desired incoming signal, includingnoise and interference.

In an optimum combining system, signals from each WT are down convertedto baseband and converted to digital signals in an ADC. Noise associatedwith the front end of the down converter and other sources is naturallyadded to the signal. The resulting signal x_(m)(k) is multiplied by acomplex weighting function w_(m)(k) and summed with similar signals fromother WT antenna elements. The resulting sum signal Σ w_(m)(k)x_(m)(k)is compared with a previously derived (and updated) reference signal(e.g., a training sequence). An error signal e(k) is generated and usedto adjust the weight values in order to minimize e(k). The objective isto derive the weighting function w_(m)(k) that enables the best matchbetween an estimated received signal and the actual transmitted signal.Alternatively, an adaptive WT array may be configured as an analog arraywherein amplitude and phase adjustments (i.e., weighting functions) areperformed at RF or IF.

In a MIMO communication system, signals transmitted from M_(T) transmitsources interfere with each other at a receiver comprising the WTs1109.1-1109.M. Thus, interference cancellation (such as matrixinversion, channel transfer function inversion, and adaptive filtering)may be employed by one or more MIMO combiners 1103.1-1103.M to separatethe signals. The received signal is expressed by:y=Hx+nwhere the received signal, y, is a vector with M_(R) terms {y_(i), i=1,. . . , N_(R)} corresponding to signals received by M_(R) (where M_(R)may have a value of 2 to M) receiver elements (i.e., WTs); x representsthe transmitted signal, which is a vector having M_(T) terms {x_(i),i=1, . . . , M_(T)} corresponding to signals transmitted by M_(T)transmitter elements; H is an M_(R)×M_(T) channel-response matrix thatcharacterizes the complex gains (i.e., transfer function, or spatialgain distribution) from the M_(T) transmission elements to the M_(R)receive elements; and n represents AWGN having zero mean and zerovariance.

In the case where the channel is characterized by flat fading, such aswhen a narrowband signal is employed (e.g., a sub-carrier of amulti-carrier signal), the elements in matrix H are scalars. Thechannel-response matrix H may be diagonalized by performing aneigenvalue decomposition of the M_(T)×M_(T) correlation matrix R, whereR=H^(H)H. Eigenvalue decomposition is expressed by:R=EDE ^(H)where E is an M_(T)×M_(T) unitary matrix with columns corresponding tothe eigenvectors e_(i) of R, and D is an M_(T)×M_(T) diagonal matrixwherein the diagonal elements are eigenvalues λ_(i) of R. The diagonalelements of D indicate the channel gain for each of the independent MIMOchannels. Alternatively, other eigenvalue-decomposition approaches, suchas singular value decomposition, may be employed.

The process for diagonalizing the MIMO channel response is initiated bymultiplying a data vector d with the unitary matrix E to produce thetransmitted vector x: x=Es. This requires the transmitter to have someinformation corresponding to the channel-response matrix H, or relatedinformation thereof. The received vector y is then multiplied withE^(H)H^(H) to provide an estimate of data vector s, which is expressedby:ŝ=E ^(H) H ^(H) y=E ^(H) HEs+E ^(H) H ^(H) n=Ds+{circumflex over (n)}where {circumflex over (n)} is AWGN having a mean vector of 0 and acovariance matrix of Λ_(n)=σ²D.

The data vector s is transformed by an effective channel responserepresented by the diagonal matrix D. Thus, there are N_(s)non-interfering subchannels wherein each subchannel i has a power gainof λ_(i) ² and a noise power of σ²λ_(i).

In the case where MIMO processing is performed on a multicarrier signal,or some other wideband signal that is spectrally decomposed intonarrowband components, eigenmode decomposition may be performed for eachfrequency bin f_(n).

If multicarrier spreading codes are employed (e.g., orthogonal DFT, orCI, codes), the channel-response matrix H can cause inter-symbolinterference between spread data symbols, even in a SISO arrangement.Accordingly, the eigenmode decomposition technique described previouslyis applicable to multicarrier spreading and despreading. In oneembodiment of the invention, eigenmode decomposition may be appliedacross two or more dimensions (e.g., both spatial and frequencydimensions). In another embodiment of the invention, eigenmodedecomposition may be applied across a single dimension (e.g., spatial orfrequency dimensions). For example, multicarrier spreading codes (forexample, orthogonal codes for data multiplexing in a givenmultiple-access channel) may be generated and processed via eigenmodedecomposition.

Any of various water-filling or water-pouring schemes may be employed tooptimally distribute the total transmission power over the availabletransmission channels, such as to maximize spectral efficiency. Forexample, water-filling can be used to adapt individual WT transmissionpowers such that channels with higher SNRs are provided withcorrespondingly greater portions of the total transmit power. Atransmission channel, as defined herein, may include a spatial (e.g., asub-space) channel, a space-frequency channel, or some other channeldefined by a set of orthogonalizing properties. Similarly, water fillingmay be used at a physically connected (i.e., wired) antenna array. Thetransmit power allocated to a particular transmission channel istypically determined by some predetermined channel-quality measurement,such as SNR, SINR, BER, packet error rate, frame error rate, probabilityof error, etc. However, different or additional criteria may be employedwith respect to power allocation, including, but not limited to, WTbattery life, load balancing, spatial reuse, power-control instructions,and near-far interference.

In conventional water filling, power allocation is performed such thatthe total transmission power P_(T) is some predetermined constant:

$P_{T} = {\sum\limits_{j \in K}{\sum\limits_{k \in L}{P_{j}(k)}}}$where L={1, . . . , N_(s)} signifies the available subspaces and K={1, .. . , N_(f)} represents the available sub-carrier frequencies f_(n). Thereceived SNR (expressed by ψ_(j)(k)) for each transmission channel isexpressed by:

${{\psi_{j}(k)} = \frac{{P_{j}(k)}{\lambda_{j}(k)}}{\sigma^{2}}},{{{for}\mspace{14mu} j} = {{\left\{ {1,\ldots\mspace{14mu},N_{s}} \right\}\mspace{14mu}{and}\mspace{14mu} k} = \left\{ {1,\ldots\mspace{14mu},N_{f}} \right\}}}$The aggregate spectral efficiency for the N_(s)N_(f) transmissionchannels is expressed by:

$C = {\sum\limits_{j = 1}^{N_{s}}{\sum\limits_{k = 1}^{N_{f}}{\log_{2}\left( {1 + {\psi_{j}(k)}} \right)}}}$

The modulation and channel coding for each transmission channel may beadapted with respect to the corresponding SNR. Alternatively,transmission channels may be grouped with respect to their data-carryingcapability. Thus, groups of transmission channels may share commonmodulation/coding characteristics. Furthermore, transmission channelshaving particular SNRs may be used for particular communication needs.For example, voice communications may be allocated to channels havinglow SNRs, and thus, data-carrying capabilities. In some cases,transmission channels that fail to achieve a predetermined threshold SNRmay be eliminated. In one embodiment of the invention, water filling isemployed such that the total transmission power is distributed overselected transmission channels such that the received SNR isapproximately equal for all of the selected channels.

An embodiment of the invention may employ reliability assessment fordetermining required processing and virtual-array size (i.e., the numberof active WTs functioning as WWAN receiver elements). Received bits orsymbols that have low reliability need more processing. Bits or symbolswith high reliability may be processed with fewer elements (WTs) orprovided with lower processing requirements. More information typicallyneeds to be combined for data streams having less reliability and lessinformation may need to be combined for data streams having morereliability. Also, nodes (WTs) with good channel quality may share moreinformation via the WLAN than nodes having poor channel quality.Optimization algorithms, such as water-filling algorithms may beemployed in the reliability domain.

FIG. 3A illustrates an embodiment of the invention in which a WLANcontroller for a WLAN group of WTs first identifies received datastreams that have the least reliability (e.g., reliability that is belowa predetermined threshold) 301. Then the WLAN controller increasesallocated processing (e.g., increases the number of receiver nodes,increases the number of processing nodes, employs a processing approachhaving higher computational complexity, etc.) 302 to those data streams.Data symbols may be combined from the smallest number of nodes such thatthe reliability of the sum is maximized, or at least exceeds apredetermined threshold reliability. The processes 301 and 302 may berepeated 303 until a predetermined result is achieved or until there isno more data left for processing.

FIG. 3B illustrates an embodiment of the invention in which a WLANcontroller identifies received data streams that have the mostreliability, or data streams having reliability that exceeds apredetermined reliability threshold 311. The WLAN controller maydecrease allocated processing (e.g., decrease the number of receivernodes, decrease the number of processing nodes, employ a processingapproach having lower computational complexity, etc.) 312 to those datastreams. The processes 301 and 302 may be repeated 303 until apredetermined result is achieved or until there is no more data left forprocessing. Embodiments of the invention may provide for encodinginformation across channels having a wide range of reliability.

Embodiments of the invention may be configured to perform blind signalseparation (BSS), such as independent component analysis. For example,A. Jourjine, S. Rickard, and O. Yilmaz, “Blind Separation of DisjointOrthogonal Signals: Demixing N Sources from 2 Mixtures,” in Proceedingsof the 2000 IEEE International Conference on Acoustics, Speech, andSignal Processing, Istanbul, Turkey, June 2000, vol. 5, pp. 2985-88,which is included herein by reference, describes a blind sourceseparation technique that allows the separation of an arbitrary numberof sources from just two mixtures, provided the time-frequencyrepresentations of the sources do not overlap. The key observation inthe technique is that for mixtures of such sources, each time-frequencypoint depends on at most one source and its associated mixingparameters.

In multi-user wireless communication systems that employ multipletransmit and receive antennas, the transmission of user informationthrough a dispersive channel produces an instantaneous mixture betweenuser transmissions. BSS may be used in such instances to separatereceived transmissions, particularly when training sequences and channelestimation are absent. In an exemplary embodiment of the invention, anOFDM-MIMO protocol may be provided across multiple independent WTs.Multiple transmissions are provided on at least one frequency channel,and frequency-domain techniques of BSS may be employed to recoverreceived signals.

In one embodiment of the invention, at least one data transmissionsource may be adapted to convey its data across the WLAN to a pluralityof WTs for transmission into the WWAN. In another embodiment of theinvention, a plurality of WTs are adapted to receive data transmissionsfrom a WWAN and couple said received data transmissions into a WLAN(with or without baseband processing) wherein centralized or distributedsignal-processing means are provided for separating the datatransmissions. Said signal-processing means includes any MIMO-processingtechniques, including multi-user detection, space-time processing,space-frequency processing, phased-array processing, optimal combining,and blind source separation, as well as others.

In one embodiment of the invention, a vector of binary data symbolsb_(i)(n) are encoded with a convolutional encoder to produce a codedsignal:s _(i)(n)=b _(i)(n)*c(n)where c(n) represents a convolutional code of length L′. A cluster of Ncoded symbols corresponding to an i^(th) user, data source, or datastream is represented by:s _(n,i)=[s _(i)(n), . . . ,s _(i)(n+N−1)]^(T)The transmit signal is generated by performing an N-point IDFT tos_(n,i) to produce:S _(n,i)=[S _(i)(n,0), . . . ,S _(i)(n,N−1)]^(T)where

${S_{i}\left( {n,k} \right)} = {\sum\limits_{m = 0}^{N - 1}{{s_{i}\left( {n + m} \right)}e^{i\; 2\;\pi\; k\;{m/N}}}}$The values S_(i)(n,k) are transmitted via at least one of N_(t) transmitantennas.

On the receive side, N_(r) receive antennas (typically, N_(r)≥N_(t)) areemployed. The signal received by a j^(th) antenna is expressed by:

${R_{j}(n)} = {{\sum\limits_{i = 1}^{N_{t}}{{S_{i}(n)}*h_{ij}}} + {n_{j}(n)}}$where n_(j)(n) represents the zero-mean AWGN introduced by the channel,and h_(ij) is the channel impulse-response of the i^(th) transmitantenna to the j^(th) receive antenna. The received signal can beinterpreted as a convolutive mixture of the coded signals, where thechannel matrix h represents the mixing system. An N-point DFT is appliedto the received signals R_(j)(n) to produce:r _(j)=[r _(j)(n), . . . ,r _(j)(n+N−1)]^(T)where

${r_{j}(n)} = {\sum\limits_{m = 0}^{N - 1}{{R_{j}\left( {n + m} \right)}e^{{- i}\; 2\;\pi\; k\;{m/N}}}}$Typically, a sufficient guard interval or cyclic prefix is employed toeliminate inter-symbol interference.

The signals from the N_(r) receiver antennas are grouped with respect tofrequency bin. An observation at a k^(th) frequency bin are expressedby:r _(n)(k)=[r ₁(n+k),r ₂(n ₊ k), . . . ,r _(N) _(r) (n+k))]^(T)=H(k)s(k)+n(k)Thus, the observations r_(n)(k) {k=0, . . . , N−1} can be interpreted asan instantaneous mixture of the transmitted signals s(k), where H(k)represents the mixing system.

There are many approaches for estimating the transmitted signals s(k)from the received signals r_(n)(k) that may be employed by the currentinvention. An exemplary embodiment of the invention employs BSStechniques. One class of BSS produces an output vector having thefollowing form:y(k)=W ^(H)(k)r _(n)(k)where W(k) is an N_(r)×N_(t) matrix that groups the coefficients of theseparating system. The output y(k) can also be expressed by:y(k)=G(k)s(k)+W ^(H)(k)n(k)where G(k)=W^(H)(k)H(k) represents the mixing/separating system. Thegoal of the separation process is to calculate the matrices W(k) so thatthe G(k) matrices are diagonal and the effects of noise W^(H)(k)n(k) areminimized. Many different approaches are applicable for achieving thesegoals.

A BSS algorithm (such as the one described in J. F. Cardoso, A.Souloumiac, “Blind Beamforming for non-Gaussian Signals,”IEEE-Proceedings-F, vol. 140, no. 6, pp. 362-370, December 1993, whichis incorporated by reference herein) may be employed to separate theinstantaneous mixture in each frequency bin. Each output at frequencybin k′ can be regarded as corresponding to a single source at bin k′multiplied by a particular gain introduce by the algorithm. The outputsy(k′) are then used as reference signals in order to recover the sourcesat frequencies k′±1. For example, the separation matrices W(k) aredetermined by minimizing the mean-square error between the outputsy(k)=W^(H)(k)r_(n)(k) and reference signals y(k′). For a given frequencybin k:W _(o)(k)=arg min_(w(k)) E└|y(k)−αy(k′)|²┘where α is a real constant, which is selected with respect to theconvolutional code:

$\alpha = \frac{\sum\limits_{p = 0}^{L - 1}{c^{2}(p)}}{\sum\limits_{p = 0}^{L - 2}{{c(p)}{c\left( {p + 1} \right)}}}$This is done to ensure G(k)=G(k′). The solution to the optimizationproblem is given by:W _(o)(k)=αR _(r) _(n) ⁻¹(k)R _(r) _(n) _(y)(k,k′)whereR _(r) _(n) (k)=E[r _(n)(k)x ^(H)(k)] andR _(r) _(n) _(y)(k,k′)=E[r _(n)(k)y ^(H)(k′)]

FIG. 4A illustrates an embodiment of the invention wherein a plurality Mof WTs 1109.1-1109.M is coupled to a MIMO processor 1103 via a WLAN1105. In this particular embodiment, a computer-processing terminal 1119may include the MIMO processor 1103. The computer processing terminal1119 may be provided with WLAN-interface functionality, and mayoptionally include WWAN-interface functionality.

The computer-processing terminal 1119 may include any of a pluralityWLAN-connected devices with signal-processing capability. For example,the computer-processing terminal 1119 may include one of the WTs1109.1-1109.M. In one aspect of the invention, the computer-processingterminal 1119 comprises a WLAN controller. In another aspect of theinvention, the computer processing terminal 1119 comprises a networkgateway, router, or access point including a CPU adapted to processsignals received from the plurality of WTs 1109.1-1109.M. Applicationsof embodiments of the invention include (but are not limited to) sensornetworks, micro-networks, RFID systems, cellular networks, and satellitenetworks.

Each WT 1109.1-1109.M may include a baseband processor 1102.1-1102.Madapted to provide WWAN baseband (or IF) signals to the MIMO processor1103 via the WLAN 1105. The MIMO processor 1103 may be configured toseparate interfering WWAN data symbols in the WWAN baseband signals. Theseparated WWAN data symbols are then coupled back to data processors1104.1-1104.M in the WTs 1109.1-1109.M.

FIG. 4B illustrates a functional embodiment of the invention in whichMIMO processing operations (represented by MIMO processors1103.1-1103.M) may be distributed over two or more WTs 1109.1-1109.M.Baseband processors 1102.1-1102.M provide WWAN baseband signals to aWLAN controller 1106, which may distribute the signals (andsignal-processing instructions) to the MIMO processors 1103.1-1103.M.The separated WWAN data symbols are then coupled back to data processors1104.1-1104.M.

FIG. 4C represents a functional embodiment of the invention. At leastone WT may provide WWAN access information 1140 to a WLAN controller.The WWAN access information typically includes necessary information(such as at least one WWAN channel assignment, authentication codes,etc.) to access at least one particular WWAN channel. The WWAN accessinformation may optionally include performance information, such as WWANchannel estimates, link-bandwidth demand, link priority, and/or WWANchannel-quality measurements (e.g., SNR, SINR, BER, PER, latency etc.).This information is typically provided to the WLAN controller by one ormore WTs.

The WLAN controller determines which WTs to activate 1141 for aparticular WWAN communication link. This may be performed for either orboth transmission and reception. The determination of which WTs will beactive 1141 in a given WWAN link typically depends on a combination offactors, including (but not limited to) the number M of WTs required toachieve predetermined channel characteristics or access parameters,which WTs have the best WWAN channel quality, load balancing,power-consumption balancing, computational overhead, latency, andWLAN-access capabilities. Accordingly, the WLAN controller may sendcontrol information via the WLAN to the WTs that includes stateinformation (e.g., operating-mode assignments, such as active, standby,sleep, and awake).

The WLAN controller may convey WWAN information to the active WTs 1142.

The WWAN information may be derived from the WWAN access information andprovided to the WTs to establish and/or maintain at least one WWAN link.Accordingly, the WWAN information may include WWAN channel assignments.The WWAN information may include beam-forming weights and/or space-timecodes. Accordingly, the step of conveying WWAN information to the WTs1142 may optionally include a preliminary signal-processing step (notshown), such as blind adaptive or deterministic weight calculation. Thispreliminary signal-processing step (not shown) may be distributed amonga plurality of the WTs, or it may be performed in a centralized mode,such as by a single computing terminal. A distributed-computing mode maytake various forms. In one mode, each of a plurality of WTs takes itsturn functioning as a computing terminal. In another mode, multiple WTsfunction as computing terminals simultaneously.

Communications in the WWAN link are coordinated between the WTs in orderto synchronize the transmitted and/or received WWAN signals 1143. Areceiver embodiment of the invention may provide for synchronizing thereceived WWAN signals, such as to provide for coherent combining. Atransmitter embodiment of the invention may provide for synchronizingthe transmitted WWAN signals from the WTs such as to enable coherentcombining at some predetermined WWAN terminal.

An optional transmitter embodiment of the invention may employsynchronization to deliberately time-offset signals arriving at one ormore WWAN terminals in order to provide for transmit diversity by theWTs. In such embodiments, one or more of the WT transmissions may beprovided with time-varying complex weights (e.g., amplitudes and/orphases), such as described in S. A. Zekavat, C. R. Nassar and S.Shattil, “Combined Directionality and Transmit Diversity via SmartAntenna Spatial Sweeping,” proceedings of 38^(th) Annual AllertonConference on Communication, Control, and Computing, University ofIllinois in Urbana-Champaign, pp. 203-211, Urbana-Champaign, Ill., USA,October 2000, S. A. Zekavat, C. R. Nassar and S. Shattil, “Smart antennaspatial sweeping for combined directionality and transmit diversity,”Journal of Communications and Networks (JCN), Special Issue on AdaptiveAntennas for Wireless Communications, Vol. 2, No. 4, pp. 325-330,December 2000, and S. A. Zekavat, C. R. Nassar and S. Shattil, “Mergingmulti-carrier CDMA and oscillating-beam smart antenna arrays: Exploitingdirectionality, transmit diversity and frequency diversity,” IEEETransactions on Communications, Vol. 52, No. 1, pp. 110-119, January2004, which are incorporated by reference herein.

In an alternative embodiment of the invention, providing WWAN accessinformation 1140 may include providing WWAN channel-performanceinformation from the WTs to at least one WWAN terminal. Thus, conveyingWWAN information to the WTs 1142 may be performed by at least one WWANterminal. An optional embodiment of the invention may provide for atleast one WWAN terminal determining which WTs in a WLAN group willoperate in a given WWAN link and conveying that WWAN information 1142 tothe WLAN group. Embodiments of the invention may provide capabilities toWWAN terminals to set up and adapt the formation of WLAN groups anddetermine which WTs are assigned to which WLAN groups. Such controlcapabilities may employ GPS positions of WTs to assist in assigning WTsto a WLAN group. Some embodiments of the invention may provide forcollaboration between a WWAN and a WLAN group for activating WTs and/orassigning WTs to the WLAN group.

In one embodiment of the invention, step 1142 may include a preliminarysignal-processing step (not shown) in which at least one WWAN terminalcalculates cooperative-beamforming weights for the WTs based onchannel-performance information provided by the WTs. Accordingly, theWWAN information may include cooperative-beamforming weights derived byat least one WWAN terminal and conveyed to at least one WT.Synchronization 1143 of the transmitted and/or received WWAN signals bythe WTs may optionally be performed by at least one WWAN terminal.Similarly, embodiments of the invention may provide for applyingtime-varying weights to WWAN-terminal transmissions (such as describedpreviously).

FIG. 4D illustrates a functional embodiment of the invention adapted toperform cooperative beamforming. WWAN channel information is provided1144 for assigning subchannels 1145 and calculating cooperativebeamforming (i.e., WT) weights 1146. The beamforming weights are thendistributed to the appropriate WTs 1147.

Sub-channel assignments 1145 are typically performed with respect to apredetermined subchannel-quality threshold, such as SNR, SINR, or BER.Subchannels having the required minimum performance may be assigned fortransmission and/or reception. Sub-channel assignments 1145 may alsoprovide for bit loading. Alternatively, sub-channel assignments 1145 maybe performed without regard to sub-channel quality. In such cases,spreading or channel coding may be performed to mitigate the effects oflost and compromised subchannels.

Weight calculations 1146 may be achieved by either deterministic orblind adaptive techniques. The calculations may be performed by one ormore WTs, or alternatively, by at least one WWAN terminal. Cooperativebeamforming weights may be provided to achieve at least one form ofarray processing benefit, including diversity combining, interferencecancellation, and spatial reuse.

FIG. 5A illustrates a functional embodiment of the invention that may beimplemented by hardware and/or software. A plurality of transmitted WWANsignals are received 1150 by a plurality of WTs. Baseband (or IF) WWANinformation is derived 1151 from the received WWAN signals. For example,in an OFDM system, a baseband WWAN signal s_(k) received by a k^(th) WTcan be represented by a linear superposition of up to M transmitted datasymbols d_(i) {i=1, . . . , M} weighted by complex channel weightsα_(ik):

$s_{k} = {{\sum\limits_{i = 1}^{M}{\alpha_{ik}d_{i}}} + \eta_{k}}$Baseband WWAN signals (which typically include the complex channelweights α_(ik)), are optionally transmitted 1158 into a WLAN fordistribution to one or more other WTs. Accordingly, data (includingbaseband WWAN signals s_(k), complex channel weights α_(ik), and/or MIMOweights β_(il)) from the one or more other WTs is received 1152 from theWLAN. MIMO processing 1153 may be performed to produce at least one setof MIMO weights β_(il) and/or estimated transmitted data symbols d_(l),which may optionally be transmitted 1159 to at least one other WT viathe WLAN. Baseband information recovery 1154 may optionally be performedon the estimated transmitted data symbols d_(i). For example, basebandoperations may include despreading, demodulation, error correction(e.g., channel decoding), demultiplexing, de-interleaving, dataformatting, etc.

FIG. 5B illustrates an alternative functional embodiment of theinvention that may be implemented by hardware and/or software. In thiscase, WWAN baseband information that does not include MIMO weights maybe received 1155 from at least one other WT via the WLAN. Thus, MIMOprocessing 1153 includes generating MIMO weights, which may betransmitted 1159 to one or more WTs via the WLAN. The functionalembodiment illustrated in FIG. 5B is particularly applicable to a WTfunctioning as a computer-processing terminal in a WLAN group. In thecase where the subject WT functions as the only MIMO-processing terminalin a given WLAN group, the functional embodiment may be characterizedsolely by steps 1155, 1153, 1154, and optional step 1159. Furthermore,the functional embodiments described herein may be adapted to performother array-processing operations in addition to, or instead of, MIMO.

FIG. 6A illustrates functional and apparatus embodiments of the presentinvention pertaining to one or more WTs, such as WT 1109. In particular,a WWAN interface 1161 may be coupled to a beam-forming system 1162,which is coupled to a WLAN interface 1163. The beam-forming system 1162may employ data received from the WLAN interface 1163 (and optionally,from data received from the WWAN interface 1161) to perform beam-formingoperations. The WLAN interface 1163 is adapted to provide WLAN datacommunications with at least one other WT (not shown). The beam-formingsystem 1162 may be adapted to provide either or both WWAN transmissionbeam-forming and reception beam-forming operations.

FIG. 6B illustrates a preferred embodiment of the invention that may beemployed as either or both apparatus and functional embodiments. A WWANinterface 1161 includes an RF front-end 1611, a DAC/ADC module 1612, apulse-shaping filter 1613, a modulator/demodulator module 1614, anequalizer modulator 1615 that optionally employs pre-equalization means,a multiplexer/demultiplexer module 1616, and a baseband-processingmodule 1617. The WWAN interface may also include a network-controlmodule 1618 that may be responsive to both WWAN control signaling andWLAN-control signals configured to convey WWAN control information tothe WWAN interface 1161.

A WLAN interface 1163 includes an RF front-end 1631, a DAC/ADC module1632, a pulse-shaping filter 1633, a modulator/demodulator module 1634,an equalizer modulator 1635 that optionally employs pre-equalizationmeans, a multiplexer/demultiplexer module 1636, and abaseband-processing module 1637. A beam-forming module 1162 is adaptedto process signals from either or both baseband modules 1617 and 1637.The beam-forming module 1162 may be adapted to process local datasymbols generated by a local data source 1160.

As described previously, the beam-forming module 1162 may be adapted toperform beam-forming operations on baseband WWAN signals received fromeither or both the WWAN interface 1161 and the WLAN interface 1163.Specifically, the beam-forming module 1162 may be adapted to performbeam forming by utilizing baseband WWAN signals, channel weights (orother channel-characterization information), beam-forming weights (suchas MIMO weights), and/or baseband data symbols. Baseband data symbolsmay be received from the local data source 1160, from local data sourceson other WTs, and/or from estimated data generated by one or moreexternal beam-forming modules (e.g., beam-forming modules on other WTs).Optionally, the beam-forming module 1162 may be configured to adjustequalization and/or pre-equalization 1615.

In an exemplary embodiment of the invention, the beam-forming module1162 is configured to process baseband WWAN signals received from thebaseband-processing module 1617 and the WLAN interface 1163. Informationoutput from the beam-forming module 1162 is conveyed to at least one ofthe WLAN interface 1163 and a local data sink 1169. Estimated WWAN datasymbols output by the beam-forming module 1162 may optionally beprocessed by the baseband-processing module 1617 or the local data sink1169. For example, the baseband-processing module 1617 may be configuredto perform various types of signal processing, including errorcorrection (such as Viterbi decoding), constellation mapping, and dataformatting on data output by the beam-forming module 1162. The resultingprocessed data may then be coupled to the local data sink 1169 and/orthe WLAN interface 1163. Alternatively, the local data sink 1169 mayperform the previously described signal-processing types.

Beam forming is performed cooperatively with other WTs to providepredetermined WWAN spatial processing for transmitted and/or receivedWWAN signals. Thus, a network-function adapter 1165 may be employed toprovide WWAN channel-access information to one or more WTs. For example,some embodiments of the invention require multiple WTs to function as asingle WT. In this case, each WT is provided with WWAN-accessinformation corresponding to the single WT it is configured to spoof.The network function adapter 1165 may be configured to generateWWAN-access information to be distributed to at least one other WTand/or it may be configured to receive WWAN-access information from theWLAN interface 1163 and convey it to the network-control module 1618 inthe WWAN interface 1161.

WWAN-access information typically includes channelization (or some otherform of multiple access) information used to transmit and/or receivedata from the WWAN. For example, WWAN-access information may take theform of user identification sequences, assigned time slots, frequencyband assignments, and/or multiple-access code assignment.

In some embodiments of the invention, a particular WT may be required tofunction as multiple WTs. In this case, WWAN-access information isconveyed to the network-control module 1618 and data is configured to beappropriately multiplexed and/or demultiplexed relative to a pluralityof multiple-access channels.

The network-function adapter 1165 may be used to convey other WWANcontrol information to WTs, including (but not limited to) power-controlcommands, timing and synchronization information, key-exchange messages,WWAN routing tables, acknowledgements, requests for retransmission,probing signals, and paging messages. The network-function adapted 1165may be configured to alter or adapt the WWAN-control information that itreceives from either or both the WWAN interface 1161 and the WLANinterface 1163. For example, WWAN power-control commands received by oneor more WTs may be adapted by the network-function adapter 1165 prior tobeing conveyed to network-control modules (such as network-controlmodule 1618) on multiple WTs. Power control may be adapted by one ormore network-function adapters 1165 for particular WTs depending ontheir WWAN channel quality and power. Alternatively, thenetwork-function adapter 1165 may adapt the number M of WTs servicing agiven link in response to WWAN control information.

In some embodiments of the invention, it may be advantageous to employ asingle decision system for network-function adaptation 1165. In one modeof operation, the network-function adapter 1165 of only one of aplurality of WTs assigned to a particular WWAN channel is adapted toconvey WWAN control information to the other WTs. In each of the otherWTs, the associated network-function adapter 1165 identifies the WWANcontrol information received from the WLAN and couples it to thenetwork-control module 1618. Thus, the network-function adapter 1165 mayinstruct the network-control module 1618 to disregard one or more typesof WWAN control information received from the WWAN interface 1161. Oneor more network-function adapters (such as network-function adapter1165) may synchronize WT responses to WWAN control information.

In another embodiment of the invention, each WT may be responsive toWWAN control information that it receives. In yet another embodiment,each of a plurality of WWAN multiple-access channels is preferablycontrolled by a separate network-function adapter 1165. These and otheradaptations and permutations of network function may be embodied byfunctional aspects of the network-function adapter 1165.

One embodiment of the invention employs the functionality of a group ofWTs corresponding to FIG. 1C with respect to the transceiver embodimentshown in FIG. 6B. In a transmission configuration, a serial data streams(n) from the local data source 1160 of a particular WT is channel codedto produce coded data stream u(n), which is grouped in blocks of size N:u(i)=[u(iN), u(iN+1), . . . , u(iN+N−1)]^(T). In this case, N is chosento equal the number M of WTs employed as antenna elements. The N−1 codeddata symbols u(n) are distributed to the other N−1 WTs via the WLANinterface 1163.

At each WT's Mux/DeMux block 1615, a particular data symbol u(n) ismapped into a frequency bin vector. In one aspect of the invention, eachdata symbol u(n) is provided with both a unique frequency bin and aunique WT, such as to achieve optimal diversity benefits. This takes theform of a frequency-bin vector having all zeros except for one bincorresponding to u(n). This scheme can be used to achieve lowtransmitted PAPR, as well as other benefits. In other embodiments,alternative WT/frequency-bin combinations may be employed. For example,multiple serial data streams s(n) may be provided to the frequency-binvector. Redundant symbols may be provided. Alternatively, the data s(n)may be spread across frequencies and/or WTs.

At each Mod/DeMod block 1614, an IFFT is applied to each data block toproduce:ũ(i)=F ^(H) u(i)where F is the N×N FFT matrix with F_(nm)=N^(−1/2)exp(−j2πnm/N). Acyclic prefix of length N_(CP) may be inserted in ũ(i) to produceũ_(CP)(i)=βT_(CP)ũ(i), which has length N_(T)=N+N_(CP). The termT_(CP)=[I_(CP) ^(T)I_(N) ^(T)]^(T) represents the cyclic prefixinsertion in which the last N_(CP) rows of the N×N identity matrix I_(N)(denoted by I_(CP)) are concatenated with identity matrix I_(N). Theterm β is the power loss factor, β=√{square root over (N/N_(T))}.

The block ũ_(CP)(i) is serialized to yield ũ_(CP)(n), which is thenpulse shaped 1613, carrier modulated 1612, amplified, and transmitted1611 via multiple antenna elements through a channel. The channelimpulse response h(n) includes the effects of pulse shaping, channeleffects, receiver filtering, and sampling.

In a receiver configuration of the invention, each of a plurality of WTsis adapted to receive a different transmitted symbol on a differentorthogonal carrier frequency. For a WT employing a square-root Nyquistreceive filter, the received samples are expressed by:x(n)=ũ _(CP)(n)*h(n)+ν(n)where ν(n) is additive white Gaussian noise (AWGN). The received samplesare grouped into blocks of size N_(T): X_(CP)(i)=[x(iN_(T)),x(iN_(T)+1), . . . , x(iN_(T)+N_(T)−1)]^(T). The first N_(CP) values ofx_(CP)(i) corresponding to the cyclic prefix are discarded, which leavesN-length blocks expressed by: x(i)=[x(iN_(T)+N_(CP)),x(iN_(T)+N_(CP)+1), . . . , x(iN_(T)+N_(T)−1)]^(T). H is defined as anN×N circulant matrix with {tilde over (H)}_(n,m)=h((n−m)_(mod N)). Theblock input-output relationship is expressed as: {tilde over(x)}(i)=β{tilde over (H)}ũ(i)+{tilde over (η)}(i), where {tilde over(η)}(i)=[ν(iN_(T)+N_(CP)), ν(iN_(T)+N_(CP)+1), . . . ,ν(iN_(T)+N_(T)−1)]^(T) is the AWGN block. Applying the FFT to {tildeover (x)}(i) yields:x(i)=F{tilde over (x)}(i)=βF{tilde over (H)}F ^(H) u(i)+{tilde over(η)}(i)=βD _(H) u(i)+η(i)whereD _(H)=diag[H(e ^(j0)),H(e ^(j(2π/N))), . . . H(e^(j(2π(N-1)/N)))]=F{tilde over (H)}F ^(H)and H(e^(j2πf)) is the frequency response of the ISI channel;

${H\left( e^{j\; 2\;\pi\; f} \right)} = {\sum\limits_{n = 0}^{N_{CP}}{{h(n)}{e^{{- j}\; 2\;\pi\; f\; n}.}}}$An equalizer followed by a decoder uses x(i) to estimate the datasymbols encoded on u(i).

Preferred embodiment of the invention may employ Spread-OFDM, whichinvolves multiplying each data block s(n) by a spreading matrix A:u(n)=As(n)In the case where CI spreading codes are employed, A_(nm)=exp(−j2πnm/N). This maps the data symbols to pulse waveforms positionedorthogonally in time. This choice of spreading codes also gives theappearance of reversing the IFFT. However, the resulting set of pulsewaveforms is a block, rather than a sequence, wherein each waveformrepresents a cyclic shift within the block duration T_(s), such asdescribed in U.S. Pat. Appl. Pubs. 20030147655 and 20040086027, whichare both incorporated by reference.

FIG. 7A illustrates a functional embodiment of the invention related tocalculating MIMO weights in a cooperative-beamforming network. Aplurality of WTs provide received baseband information from a WWANchannel 1701 that includes a training sequence and/or a data sequencehaving a predetermined constellation of values. WWAN MIMO processing isperformed 1702 on the received baseband information to derive aplurality of array-processing weights which are then distributed 1703via the WLAN to a predetermined plurality of WTs.

FIG. 7B illustrates a functional embodiment of the invention adapted tocalculate transmitted data symbols received by a cooperative-beamformingnetwork. A plurality of WTs provide received baseband information from aWWAN channel 1701 that includes a data sequence having a predeterminedconstellation of values. WWAN MIMO processing may be performed 1704 onthe received baseband information to derive a plurality of estimateddata symbols d_(i), which are then conveyed 1705 via the WLAN to atleast one destination WT. The WWAN MIMO processing 1704 may optionallyinclude providing for any of a set of signal-processing operations,including filtering, demodulation, demultiplexing, error correction, anddata formatting.

FIG. 8A illustrates a functional embodiment for a method and apparatusof the invention. Specifically, a data source 1800 is adapted todistribute a plurality of data symbols via a WLAN channel 199 to aplurality N_(t) of WTs 1806.1-1806.N_(t), which are adapted to transmitthe data symbols into at least one WWAN channel 99. Although thefunctional embodiment shown in FIG. 8A is illustrated with respect touplink WWAN functionality, the functional blocks may alternatively beinverted to provide for downlink WWAN functionality.

The data source and the WTs 1806.1-1806.N_(t) include appropriateWLAN-interface equipment to support distribution of the data symbols tothe WTs 1806.1-1806.N_(t). For example, the WTs 1806.1-1806.N_(t) areshown including WLAN-interface modules 1801.1-1801.N_(t). The WLANchannel 199 may optionally include additional network devices that arenot shown, such as routers, access points, bridges, switches, relays,gateways, and the like. Similarly, the data source 1800 and/or the WTs1806.1-1806.N_(t) may include one or more said additional networkdevices. The data source 1800 may include at least one of the WTs1806.1-1806.N_(t).

A coder 1803.1-1803.N_(t) in each of the WTs 1806.1-1806.N_(t) isadapted to receive a baseband data sequence from the associatedWLAN-interface module 1801.1-1801.N_(t) and provide coding, such aschannel coding, spreading, and/or multiple-access coding. A coded datasequence output from each coder 1803.1-1803.N_(t) is mapped intofrequency bins of multicarrier generators, such as IDFTs1804.1-1804N_(t). This embodiment may be employed to producemulticarrier signals or to synthesis single-carrier signals from aplurality of spectral components. Alternatively, other types ofmulticarrier generators may be employed, such as quadrature-mirrorfilters or DSPs configured to perform other transform operations,including Hadamard transforms. The resulting multicarrier signals arecoupled into the WWAN channel 99 by associated WWAN-interface modules1805.1-1805.N_(t).

For each flat-fading subcarrier frequency channel, the WWAN channel maybe characterized by channel responses 1890.1-1890-N_(t) and1899.1-1899-N_(t) of a mixing system. The channel responses1890.1-1890-N_(t) and 1899.1-1899-N_(t) represent elements of H, anN_(r)×N_(t) channel-response matrix that characterizes the complex gains(i.e., transfer function, or spatial gain distribution) from the N_(t)transmission elements to the N_(r) receive elements; and n_(i)(n)represents an AWGN contribution having zero mean and zero variance.

There are N_(r) receiver elements comprising WWAN-interface modules1815.1-1815.N_(r) and filter banks, such as DFTs 1814.1-1814.N_(r),coupled to at least one MIMO combiner 1810. The MIMO combiner 1810 isadapted to perform any number of signal-processing operations, includingdecoding received data symbols. In one embodiment of the invention, theMIMO combiner 1810 is adapted to perform diversity combining. In anotherembodiment of the invention, the MIMO combiner 1810 is adapted toperform spatial (e.g., sub-space) processing. Furthermore, many otherapplications and embodiments of the invention may be achieved using thefunctional description (or minor variations thereof) depicted in FIG.8A.

FIG. 8B illustrates a functional embodiment of the invention that may beincorporated into specific apparatus and method embodiments. Inparticular, WWAN signals received from a WWAN channel 99 by a pluralityN_(r) of WTs 1836.1-1836.N_(r) are conveyed via a WLAN channel 199 to aMIMO combiner 1830.

In this case, WWAN data symbols are encoded by one or more coders (suchas coders 1821.1-1821.N_(t)), impressed on a plurality of subcarriers byIDFTs 1822.1-1822.N_(t), and coupled into the WWAN channel 99 by aplurality of WWAN-interface modules 1825.1-1825.N_(t). Received WWANsignals may be coupled from the WWAN channel 99 by a plurality N_(r) ofWTs 1836.1-1836.N_(r). Each WT 1836.1-1836.N_(r) includes at least oneWWAN-interface module (such as WWAN-interface modules1831.1-1831.N_(r)), a filter bank (such as DFTs 1834.1-1834.N_(r)), anda WLAN-interface module (such as 1835.1-1835.N_(r)).

WWAN signals received by each WT 1836.1-1836.N_(r) are converted to abaseband data sequence, separated into frequency components (by the DFTs1834.1-1834.N_(r)), and then adapted for transmission into the WLANchannel 99. A MIMO combiner 1830 may be configured to receive WLANtransmissions, recover the frequency components, and perform MIMOprocessing to generate estimates of the transmitted WWAN data symbols.The MIMO combiner 1830 and/or the WTs 1836.1-1836.N_(r) may be adaptedto perform decoding. In one embodiment of the invention, the MIMOcombiner 1830 may include one or more of the WTs 1836.1-1836.N_(r).

FIG. 8C illustrates an embodiment of the invention in which WTs1836.1-1836.N_(r) are adapted to perform time-domain (e.g., Rake)processing. Specifically, each WT 1836.1-1836.N_(r) includes a Rakereceiver 1854.1-1854.N_(r). The embodiment illustrated in FIG. 8C isparticularly suited to performing MIMO operations on receiveddirect-sequence signals, such as direct sequence CDMA (DS-CDMA) signals.

Particular embodiments of the invention may be directed towardtransmitting and/or receiving any of the well-known types of spreadsignals. Spread signals include spread-spectrum signals in which atransmitted signal is spread over a frequency band much wider than theminimum bandwidth needed to transmit the information being sent. Spreadspectrum includes direct-sequence modulation commonly used in CDMAsystems (e.g., cdmaOne, cdma2000, 1×RTT, cdma 1×EV-DO, cdma 1×EV-DV,cdma2000 3×, W-CDMA, Broadband CDMA, and GPS), as well asfrequency-domain spreading techniques, such as spread-OFDM,multi-carrier CDMA, and multi-tone CDMA.

In a DS-CDMA system, a k^(th) WWAN transmission signal s^(k)(t) thatincludes N code bits {b^(k)[n]}_(n=1) ^(N) is given by:

${s^{k}(t)} = {\sum\limits_{n = 0}^{N - 1}{{b^{k}\lbrack n\rbrack}{g_{T_{b}}\left( {t - {nT}_{b}} \right)}{g_{\tau}(t)}{a^{k}\left( {t - {iT}_{b}} \right)}{\cos\left( {2\;\pi\; f_{c}t} \right)}}}$where

${{a^{k}(t)} = {\sum\limits_{i = 0}^{G - 1}{C_{i}^{k}{g_{T_{c}}\left( {t - {iT}_{c}} \right)}}}},{C_{i}^{k} \in \left\{ {{- 1},1} \right\}}$is the DS spreading signal, G represents processing gain, T_(c) is thechip duration, T_(b) is the bit duration, and g_(T) _(c) (t), g_(T) _(b)(t), and g_(r)(t) represent the chip, bit, and transmitted pulse shapes,respectively.

A plurality M of WTs linked together by a WLAN comprises elements of anM-element antenna array capable of receiving K≤M transmission channels.In a frequency-selective channel, the received signal at the array is:

${r(t)} = {{\sum\limits_{k = 1}^{K}{\sum\limits_{l = 0}^{L^{k} - 1}{\sum\limits_{n = 0}^{N - 1}{\alpha_{l}^{k}{\overset{\rightarrow}{V}\left( \vartheta_{l}^{k} \right)}{b_{k}\lbrack n\rbrack}{g\left( {t - \tau_{l}^{k} - {nT}_{b}} \right)}{\cos\left( {{2\pi\; f_{c}t} + \varphi_{l}^{k}} \right)}}}}} + {\upsilon(t)}}$where {right arrow over (V)}(ϑ) is an array-response vector, K is thenumber of received transmission channels, L^(k) is the number ofdistinct fading paths corresponding to the k^(th) user, α_(l) ^(k) isthe fade amplitude associated with path l and user k, φ_(l) ^(k)=U[0,2π]represents the associated fade phase, τ_(l) ^(k) is the path time-delay(which occurs below a predetermined duration threshold T_(max)), andϑ_(l) ^(k) denotes angle of arrival. The array response vector {rightarrow over (V)}(ϑ) is expressed by:{right arrow over (V)}(ϑ)=[1 e ^(−2πd) ¹ ^(cos θ/λ) . . . e ^(−2πd)^(M-1) ^(cos θ/λ)]where d_(m) is the antenna separation, and λ is the wavelengthcorresponding to carrier frequency f_(c). For a j^(th) user's l^(th)path, the n^(th) bit at the beamformer output is given by:

z_(l)^(j)[n] = W^(H)(ϑ_(l)^(k))∫_(+(n − 1)T_(b))^(+nT_(b))r(t)cos (2π f_(c)t + φ_(l)^(j))a^(j)(t − τ_(l)^(j) − (n − 1)T_(b)) dtwhere W(ϑ_(l) ^(k)) is the weighting vector of the beamforming system.z_(l) ^(k)[n] can be expressed by four components:z _(l) ^(k)[n]=S _(i) ^(j)[n]+ISI _(i) ^(j)[n]+IXI _(i) ^(j)[n]+υ_(i)^(j)[n]where S is the desired signal, ISI is inter-symbol interference, IXI iscross interference (i.e., multiple-access interference), and ν is theAWGN contribution. These components can be expressed as follows:S _(l) ^(j)[n]=α_(l) ^(j) W ^(H)(ϑ_(l) ^(j)){right arrow over (V)}(ϑ_(l)^(j))b ^(j)[n]G

$\begin{matrix}{{{ISI}_{i}^{j}\lbrack n\rbrack} = {\sum\limits_{\underset{h \neq l}{h = 0}}^{L^{k} - 1}{\sum\limits_{n = 0}^{N - 1}{\alpha_{l}^{k}{W^{H}\left( \vartheta_{h}^{j} \right)}{\overset{\rightarrow}{V}\left( \vartheta_{l}^{k} \right)}{b^{j}\lbrack n\rbrack}{\cos\left( {\varphi_{h}^{j} - \varphi_{l}^{j}} \right)}{R_{jj}\left( {\tau_{h}^{j} - \tau_{l}^{j} - {nT}_{b}} \right)}}}}} \\{{{IXI}_{i}^{j}\lbrack n\rbrack} = {\sum\limits_{\underset{k \neq j}{k = 1}}^{K}{\sum\limits_{\underset{h \neq l}{h = 0}}^{L^{k} - 1}{\sum\limits_{n = 0}^{N - 1}{\alpha_{l}^{k}{W^{H}\left( \vartheta_{h}^{k} \right)}{\overset{->}{V}\left( \vartheta_{l}^{j} \right)}{b^{j}\lbrack n\rbrack}{\cos\left( {\varphi_{h}^{k} - \varphi_{l}^{j}} \right)}{R_{kj}\left( {\tau_{l}^{j} - \tau_{h}^{k} - {nT}_{b}} \right)}}}}}} \\{\mspace{79mu}{{\upsilon_{l}^{j}\lbrack n\rbrack} = {\int_{{+ {({n - 1})}}T_{b}}^{+ {nT}_{b}}{{W^{H}\left( \vartheta_{l}^{j} \right)}{n(t)}{a^{j}\left( {t - \tau_{l}^{j}} \right)}{\cos\left( {{2\pi\; f_{c}t} + \varphi_{l}^{j}} \right)}\ {dt}}}}}\end{matrix}$where W^(H)(ϑ_(l) ^(j)){right arrow over (V)}(ϑ_(l) ^(j)) represents thespatial correlation, φ_(l) ^(j) and τ_(l) ^(j) are the random phase andtime delay for the j^(th) user's l^(th) path, G is the processing gain,and R_(jj) and R_(kj) are the partial auto-correlation andcross-correlation of the direct sequence code(s):

R_(kj)(τ) = ∫_(τ)^(T)a^(k)(t)a^(j)(t − τ) dtMaximal ratio combining produces an output:

${z^{j}\lbrack n\rbrack} = {\sum\limits_{l = 0}^{L - 1}{\alpha_{l}^{j}{z_{l}^{j}\lbrack n\rbrack}}}$which can be processed by a decision processor. In this case, the BER isgiven by:

$P_{e} = {\int_{0}^{\infty}{{Q\left( {2r_{o}} \right)}{f\left( r_{o} \middle| {\overset{\_}{r}}_{o} \right)}\ {dr}_{o}}}$where r _(o) is the mean value of the instantaneous SINR, r_(o), and Q() represents the complementary error function.

It should be appreciated that the WTs may be adapted to perform eitheror both time-domain (e.g., Rake) or frequency-domain processing as partof a receiver operation. Signals received by a plurality of WTs may becombined with respect to any combining technique, including EGC, MRC,Minimum Mean Squared Error Combining, other types of optimal combining,Successive Interference Cancellation, and other matrix-reduction/matrixdiagonalization techniques. Array-processing operations may includecombinations of local and global processing. For example, diversitycombining may be performed at each multi-element WT. Then signals fromeach WT may be combined (e.g., in a central processor) to performsub-space (e.g., directional) processing. Other combinations of localand global processing may be employed. Similarly, combinations ofsub-space processing (i.e., capacity enhancement) and diversitycombining (i.e., signal-quality enhancement) may be performed. It shouldalso be appreciated that the WTs may be adapted to perform either orboth time-domain and frequency-domain processing for transmission. Thus,appropriate delays or complex weights may be provided to WTtransmissions to produce a coherent phase front that converges at apredetermined WWAN destination node.

FIG. 9A illustrates an optional transmission embodiment of the presentinvention. That is, method and apparatus configurations can be inferredfrom the following descriptions. A data source 1900 is adapted toprovide data for processing by an array processor, such as MIMOprocessor 1902. Optionally, other types of array processors may beprovided. A physical (e.g., wired) connection 1902 and/or a wirelessconnection 1901 couple the data between the data source 1900 and theMIMO processor 1902. The wireless connection 1901 is enabled by a WLAN1999. The MIMO processor 1902 is adapted to provide MIMO processing tothe data, such as providing complex channel weights, providing spreadingweights, and/or providing channel coding.

In one exemplary embodiment of the invention, MIMO processor 1902provides convolutional or block channel coding to the data, whicheffectively spreads each data bit over multiple coded data bits. Theresulting coded data bits are then grouped in serial blocks by the MIMOprocessor 1902. Signal-block outputs from the MIMO processor 1902 areprovided with serial-to-parallel conversion by the WLAN 1999 (which isdenoted by S/P 1914) and distributed to a plurality of WTs1906.1-1906.M.

Each WT 1906.1-1906.M has a WLAN interface 1907.1-1907.M adapted toreceive and demodulate the data received from the MIMO processor 1902.The MIMO processor 1902 is accordingly equipped with a WLAN interfacethat is not shown. The MIMO processor 1902 is typically comprised of oneor more WTs 1906.1-1906.M. In some embodiments of the invention, MIMOprocessor 1902 may include at least one computer-processing terminalthat does have a WWAN interface.

Data received from the MIMO processor 1902 is then modulated1908.1-1908.M by each WT 1906.1-1906.M for transmission into a WWANchannel by a corresponding WWAN interface 1909.1-1909.M. Modulation1908.1-1908.M typically includes mapping blocks of data bits to datasymbols, which are then mapped to a modulation constellation. Modulation1908.1-1908.M may also include channel coding and/or data interleaving.In an exemplary embodiment of the invention, modulation 1908.1-1908.Mincludes the application of complex WWAN channel weights. Such channelweights may optionally be provided by the MIMO processor 1902. Inalternative embodiment of the invention, modulators 1908.1-1908.Mprovide a predetermined delay profile (provided by the MIMO processor1902) to the data to be transmitted into the WWAN channel.

FIG. 9B illustrates a functional flow chart that pertains to transmitterapparatus and method embodiments of the invention. One or more datasources 1920.1-1920.K are coupled via a WLAN 1999 to a plurality M ofWTs 1926.1-1926.M. Each WT 1926.1-1926.M includes a WLAN interface1927.1-1927.M, an array processor (such as a MIMO processor1926.1-1926.M), and a WWAN interface 1929.1-1929.M.

The data sources 1920.1-1920.K optionally include baseband-processingcapabilities, such as channel coding, interleaving, spreading,multiplexing, multiple-access processing, etc. The data sources1920.1-1920.K include WLAN interfaces (not shown). The data sources1920.1-1920.K may include one or more WTs 1926.1-1926.M.

The WLAN interfaces 1927.1-1927.M include apparatus and means forconverting received signals that were formatted for transmission in theWLAN 1999 into baseband data signals. The MIMO processors 1926.1-1926.Mare adapted to provide for frequency-domain and/or time-domain MIMOoperations on the baseband data signals received from the WLANinterfaces 1927.1-1927.M. Alternatively, the MIMO processors1926.1-1926.M may be adapted to perform phase operations at WWAN carrierfrequencies transmitted by the WWAN interfaces 1929.1-1929.M. The WWANinterfaces 1929.1-1929.M provide any necessary baseband, IF, and RFoperations necessary for transmitting data in a WWAN channel.

FIG. 10A illustrates software components of a transmission embodiment ofthe invention residing on a computer-readable memory 1950. Anarray-processing weighting source-code segment 1951 is adapted togenerate a plurality of array-element weights for an antenna arraycomprised of a plurality of WTs coupled to at least one WWAN. Thearray-element weights may include at least one of frequency-domainweights (e.g., complex sub-carrier weights) and time-domain weights(e.g., weighted Rake taps). The array-processing weighting source-codesegment 1951 is adapted to accept as input at least one of a set ofinformation inputs, including data signals for transmission into theWWAN, training signals (e.g., known transmission symbols) received fromthe WWAN, data signals (e.g., unknown transmission symbols) receivedfrom the WWAN, WWAN channel estimates, and WWAN-control information.

The array-processing weighting source-code segment 1951 is adapted toprovide as output at least one of a set of information signals,including WWAN weights and weighted data for transmission into the WWAN(i.e., weighted WWAN data). A WLAN distribution source code segment 1952is provided for distributing either or both WWAN weights and weightedWWAN data received from source-code segment 1951 to a plurality of WTsvia at least one WLAN. The WLAN distribution source code segment 1952may optionally function to couple at least one of a set of informationinputs to the source-code segment 1951, including data signals fortransmission into the WWAN (such as generated by other WTs), trainingsignals received from the WWAN, data signals received from the WWAN,WWAN channel estimates, and WWAN-control information.

FIG. 10B illustrates software components of a receiver embodiment of theinvention residing on a computer-readable memory 1960. Anarray-processing weighting source-code segment 1961 is adapted togenerate a plurality of array-element weights for an antenna arraycomprised of a plurality of WTs coupled to at least one WWAN. Thearray-element weights may include at least one of frequency-domainweights (e.g., complex sub-carrier weights) and time-domain weights(e.g., weighted Rake taps). The array-processing weighting source-codesegment 1961 is adapted to accept as input at least one of a set ofinformation inputs, including training signals (e.g., known transmissionsymbols) received from the WWAN, data signals (e.g., unknowntransmission symbols) received from the WWAN, WWAN channel estimates,and WWAN-control information.

The array-processing weighting source-code segment 1961 is adapted toprovide as output at least one of a set of information signals,including WWAN weights, weighted received WWAN data for transmissioninto the WLAN (i.e., weighted received WWAN data), weighted WWAN datareceived from a plurality of WTs connected by the WLAN and then combined(i.e., combined weighted WWAN data), and estimates of said combinedweighted WWAN data. A WLAN distribution source code segment 1962 isprovided for distributing at least one of a set of signals (includingthe WWAN weights, the weighted received WWAN data, the combined weightedWWAN data, and the estimates said combined weighted WWAN data) to aplurality of WTs via at least one WLAN. The WLAN distribution sourcecode segment 1962 may optionally function to couple at least one of aset of information inputs to the source-code segment 1961, includingWWAN data signals received by other WTs, training signals received fromthe WWAN by other WTs, WWAN channel estimates (either of both locallygenerated and received from other WTs), WWAN-control information,weights received from at least one other WT, and weighted WWAN datareceived from at least one other WT.

Since software embodiments of the invention may reside on one or morecomputer-readable memories, the term computer-readable memory is meantto include more than one memory residing on more than one WT. Thus,embodiments of the invention may employ one or moredistributed-computing methods. In one embodiment of the invention, thecomputer-readable memory 1950 and/or 1960 further includes adistributed-computing source-code segment (not shown). It will beappreciated that many different types of distributed computing, whichare well known in the art, may be performed. The WLAN distributionsource code segment 1952 and/or 1962 may be adapted to provide forsynchronizing transmitted and/or received WWAN signals.

Embodiments of the invention described herein disclose array-processingmethods (including software implementations) and apparatus embodimentsemployed in a WWAN and coordinated between a plurality of WTs connectedvia at least one WWAN. WTs in a WLAN group typically share the same WWANaccess. However, some embodiments of the invention provide for WTs withaccess to different WWANs. Furthermore, one or more WTs may have accessto a plurality of WWANs and WWAN services. In some cases, one or moreWTs may not be configured to access any WWAN.

In some embodiments of the invention, the computer-readable memory 1950and/or 1960 further includes a WLAN setup source-code segment (notshown) capable of establishing and/or dynamically reconfiguring at leastone WLAN group. For example, WTs may convey location information (e.g.,GPS) and/or signal-strength information (e.g., in response to a WLANprobing signal) to the WLAN setup source-code segment (not shown). TheWLAN setup source-code segment (not shown) may reside on one or more ofthe WTs and/or at least one WWAN terminal, such as a cellular basestation.

The WLAN setup source-code segment (not shown) may provide one or moreWLAN group configuration functions, including determining the number ofWWAN-enabled WTs, the total number of WTs in the WLAN group, which WTsare active (and inactive), which WTs are in the WLAN group, andselecting which WT(s) has (have) network-control functionality. The WLANsetup source-code segment (not shown) may be adapted to perform WWANchannel quality analysis functions, including determining WWAN linkperformance (relative to one or more WTs) from training sequences orpilot signals, performing WWAN-channel estimation, receiving linkperformance or channel estimates from the WWAN, and performingchannel-quality calculations (e.g., SNR, BER, PER, etc.).

The WLAN setup source-code segment (not shown) may select which WTs areWWAN-enabled based on one or more criteria points, including WWAN linkperformance, WLAN link performance, required transmission and/orreception needs (e.g., the number of WLAN-group WTs requesting WWANservices, the types of WWAN services required, individual and totalthroughput, required signal-quality threshold, and WWAN bandwidthavailable to the WLAN group), computational load, WLAN capacity,power-consumption load, diversity gain, and interference mitigation.

The WLAN distribution source code segments 1952 and 1962 may be adaptedto route WWAN channel-access information to the WTs. For example, WWANchannel-access information can include multiple-access information(e.g., multiple-access codes, frequency bands, time slots, spatial (orsub-space) channels, etc.), power control commands, timing andsynchronization information, channel coding, modulation, channelpre-coding, and/or spread-spectrum coding.

FIG. 11 shows a WWAN comprising a WWAN access point (e.g., a basestation) 2120 and a local group 2100 comprising a plurality of wirelessterminals (WTs) 2101-2104 communicatively coupled together via a WLAN2105. A network-management operator 2106 is configured to handleWWAN-control operations within the local group 2100. In an exemplaryembodiment, the network-management operator 2106 is coupled to at leastone of the WTs 2101-2104 (e.g., WT 2103). One or more of the WTs2101-2104 may be configured to transmit and/or receive WWANcommunication signals, such as WWAN traffic channels 2110 and WWANcontrol messages 2111. Signals in the WWAN traffic channels 2110 may beprocessed by one or more of the WTs 2101-2104, which may include atleast one local area network controller (e.g., 2103). The WWAN controlmessages 2111 are processed by the network-management operator 2106.

In an exemplary embodiment of the invention, a target WT (e.g., WT 2104)communicates with one or more WTs in the local group 2100 via the WLAN2105, and the local group 2100 is configured to communicate with thebase station 2120 via the WWAN. More specifically, one or more of theWTs 2101-2104 may be configured to participate in WWAN communications atany particular time. The target WT 2104 may communicate with the networkcontroller (e.g., WT 2103), which is configured to communicate withother WTs in the local group 2100. The network controller 2103 typicallyoversees network control functions in the local area network.Alternatively, the target WT 2104 may function as a local area networkcontroller. A particular WT may determine which WTs to use fortransmitting and/or receiving signals in the WWAN based on local areanetwork criteria, as well as WWAN-related criteria. Local area networkcontrol and/or WWAN control functionality may be distributed between oneor more WTs in the local group.

For the purpose of the present disclosure, a WWAN comprising a pluralityof wireless terminals communicatively coupled together via a WLAN may bedefined as one or more of the following system configurations:

-   -   A plurality of WTs in a local group configured to receive from a        base station a signal intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        base station a plurality of signals modulated on interfering        (e.g., common) channels and intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        base station a plurality of signals modulated on different        non-interfering channels and intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        plurality of base stations a signal modulated on a common        channel intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        plurality of base stations a signal redundantly modulated on a        plurality of different channels intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        plurality of base stations a plurality of signals modulated on        interfering channels and intended for at least one WT.    -   A plurality of WTs in a local group configured to receive from a        plurality of base stations a plurality of signals modulated on        different non-interfering channels and intended for at least one        WT.    -   A plurality of WTs in a local group configured to transmit to a        base station a signal originating from at least one WT.    -   A plurality of WTs in a local group configured to transmit to a        base station a plurality of signals modulated on interfering        (e.g., common) channels originating from at least one WT.    -   A plurality of WTs in a local group configured to transmit to a        base station a plurality of signals modulated on different        non-interfering channels originating from at least one WT.    -   A plurality of WTs in a local group configured to transmit to a        plurality of base stations a signal modulated on a common        channel originating from at least one WT.    -   A plurality of WTs in a local group configured to transmit to a        plurality of base stations a signal redundantly modulated on a        plurality of different channels originating from at least one        WT.    -   A plurality of WTs in a local group configured to transmit to a        plurality of base stations a plurality of signals modulated on        interfering channels originating from at least one WT.    -   A plurality of WTs in a local group configured to transmit to a        plurality of base stations a plurality of signals modulated on        different non-interfering channels and originating from at least        one WT.    -   A plurality of WTs in a first local group configured to receive        from a second local group a signal intended for at least one WT        in the first local group.    -   A plurality of WTs in a first local group configured to receive        from a second local group a plurality of signals modulated on        interfering channels and intended for at least one WT in the        first local group.    -   A plurality of WTs in a first local group configured to receive        from second local group a plurality of signals modulated on        different non-interfering channels and intended for at least one        WT in the first local group.    -   A plurality of WTs in a first local group configured to transmit        to a second local group a signal originating from at least one        WT in the first local group.    -   A plurality of WTs in a first local group configured to transmit        to a second local group a plurality of signals modulated on        interfering channels and originating from at least one WT in the        first local group.    -   A plurality of WTs in a first local group configured to transmit        to a second local group a plurality of signals modulated on        different non-interfering channels and originating from at least        one WT in the first local group.    -   A base station comprising a plurality of WTs in a base station        local group configured to transmit a signal intended for at        least one subscriber WT not in the base station local group.    -   A base station comprising a plurality of WTs in a base station        local group configured to transmit a plurality of signals        modulated on interfering (e.g., common) channels and intended        for at least one subscriber WT not in the base station local        group.    -   A base station comprising a plurality of WTs in a base station        local group configured to transmit a plurality of signals        modulated on different non-interfering channels and intended for        at least one subscriber WT not in the base station local group.    -   Multiple base stations comprising at least one base station        local group configured to transmit a signal modulated on a        common channel intended for at least one WT.    -   Multiple base stations comprising at least one base station        local group configured to transmit to a plurality of WTs a        signal redundantly modulated on a plurality of different        channels intended for at least one WT.    -   Multiple base stations comprising at least one base station        local group configured to transmit to a plurality of WTs a        plurality of signals modulated on interfering channels and        intended for at least one WT.    -   Multiple base stations comprising at least one base station        local group configured to transmit to a plurality of WTs a        plurality of signals modulated on different non-interfering        channels and intended for at least one WT.    -   A base station comprising a plurality of WTs in a base station        local group configured to receive a signal originating from at        least one WT.    -   A base station comprising a plurality of WTs in a base station        local group configured to receive a plurality of signals        originating from at least one WT and modulated on interfering        channels.    -   A base station comprising a plurality of WTs in a base station        local group configured to receive a plurality of signals        modulated on different non-interfering channels and originating        from at least one WT.    -   Multiple base stations comprising at least one base station        local group configured to receive a signal modulated on a common        channel originating from at least one WT.    -   Multiple base stations comprising at least one base station        local group configured to receive a signal redundantly modulated        on a plurality of different channels originating from at least        one WT.    -   Multiple base stations comprising at least one base station        local group configured to receive a plurality of signals        modulated on interfering channels and originating from at least        one WT.    -   Multiple base stations comprising at least one base station        local group configured to receive a plurality of signals        modulated on different non-interfering channels and originating        from at least one WT.

A network-management operator may include a single WT or a plurality ofWTs. In one embodiment, the network-management operator includes asingle WT communicatively coupled to the WWAN and configured to performWWAN-control operations for one or more WTs in the local group. Thus,the network-management operator may be configured to transmit and/orreceive WWAN-control parameters in the WWAN on behalf of one or more WTsin the local group. A local area network controller may function as anetwork-management operator for one or more WTs in the group.

Each WT may function as its own network-management operator. Forexample, a WT functioning as its own network-management operator may becommunicatively coupled to the WWAN and configured to transmit andreceive WWAN control information directly with the WWAN, whereastraffic-channel processing may be performed in cooperation with one ormore other WTs in the local group. In another exemplary configuration,WWAN control information may be coupled from a target WT (e.g., a sourceor destination WT relative to the subject information, i.e., the WWANcontrol information) to a relay WT communicatively coupled to the WWANand configured to transmit and receive the target WT's WWAN controlinformation. While the target WT functions as its own network-managementoperator, it may employ other WTs in the local group to transmit andreceive WWAN control messages. Thus, the relay WT may merely function asa pass through having optional added physical-layer adjustments for theWWAN control information. The physical-layer adjustments may be used tocondition the WWAN control messages for the WWAN channel and/or the WLANchannel. Similarly, a WT functioning as a network-management operatorfor itself and/or at least one other WT may employ one or more WTs inthe local group for transmitting and receiving WWAN control messages inthe WWAN.

In another embodiment, a WT may function as a network-managementoperator for one or more other WTs. For example, a network controllermay function as a network-management operator for at least one other WT.In another embodiment, at least one WT that is neither a networkcontroller nor a target WT may function as the network-managementoperator. For example, a WT having the best WWAN channel (such as may bedetermined by any of a variety of signal quality criteria that are wellknown in the art) may be selected as the network-management operator.Various criteria for selecting WTs for network-management operatorresponsibilities may be implemented, including load balancing.

In another embodiment of the invention, a plurality of WTs in a localgroup may simultaneously function as a network-management operator. Thenetwork-management operator may comprise multiple WTs including a targetWT, multiple WTs including a network controller, multiple WTs notincluding a network controller, or multiple WTs not including a targetWT. A plurality of WTs may redundantly process WWAN control messages.Alternatively, each of a plurality of WTs configured to performWWAN-control operations may be configured to perform a predeterminedsubset of the WWAN-control operations.

A network-management operator may participate in any combination ofvarious WWAN-control operations, including power control, data-ratecontrol, session control, authentication, key exchange, paging,control-channel monitoring, traffic channel request, channel assignment,error detection, acknowledgement, request for retransmission,identification, reconnects, synchronization, flow control, request forservice from a particular sector or access point, hand-off.

The Open Systems Interconnection Reference Model (OSI Reference Model)may be used to describe the function of a WWAN comprising a local groupof a plurality of WTs communicatively coupled together via a WLAN.

In the Application Layer, each WT typically employs its own userapplications for accessing network services (e.g., login, data upload,data download, multi-media processing). Thus, each WT handles its ownapplication-layer network access, flow control, and error processing.Each WT controls its own user interface for access to services thatsupport user applications. These applications typically are not subjectto cooperative access (e.g., sharing). However, certain networkresources (e.g., printers, faxes) may be shared. Some applications, suchas computational processing applications, may provide for distributedcomputing processes between WTs in a network. However, suchdistributed-computing applications have not been employed in the priorart for receiving and decoding wireless communications.

In the Presentation Layer, each WT may translate data from anapplication format to a network format and vice-versa. Different dataformats from different applications are processed to produce a commondata format. Each WT may manage its own protocol conversion, characterconversion, data encryption/decryption, and data compression/expansion.Alternatively, a network controller that serves multiple WT may performone or more presentation-layer functions. For example, data-processingintelligence may be handled by a network controller, and individual WTsmay function as dumb terminals. In some multimedia applications, anetwork controller may function essentially as a media server configuredto deliver predetermined data formats to each WT functioning as a mediadevice. Furthermore, there are various degrees of how presentation-layerprocessing may be shared between WTs and a network controller.

In the Session Layer, each WT may be responsible for identification soonly designated parties can participate in a session. Session setup,reconnects, and synchronization processes may be managed by the targetWT (e.g., a subscriber, an access point, or a base station), whichfunctions as its own network-management operator for session-layerprocessing. Alternatively, a network controller may manage session-layeractivities for each of one or more WTs in the local group. The networkcontroller may store identities for each WT and manage sessions and theflow of information for each WT.

In another embodiment, multiple WTs may participate in sessionmanagement. Some centralized decision-processing (such as by the targetWT or a network controller) may be employed to direct one or more WTs toperform specific session-layer activities. Multiple responsibilities maybe divided among the WTs. For example, one WT may conductsynchronization processes and another WT may perform session setup. TheWTs assigned to perform particular functions may change with respect tosignal quality with the WWAN, load balancing criteria, and/or otherconsiderations.

In the Transport Layer, each WT may convert data streams into packets orpredetermined segments. Each WT may also process received packets toreassemble messages. Thus, each WT may perform its own error handling,flow control, acknowledgement, and request for retransmission.

Alternatively, a network controller may manage transport-layeroperations for each of one or more WTs in a local group. The networkcontroller may be configured to convert data streams received from theWTs into packets. Similarly, the WT may convert data packets receivedfrom the WWAN into data streams that are routed to the appropriate WTs.The network controller may perform common network-management operatorfunctions, including error handling, flow control, acknowledgement, andrequest for retransmission for each of the WTs.

In yet another embodiment, multiple WTs may be used to convert datastreams into packets and/or process received packets to reassemblemessages for a particular target WT. Each of a plurality of WTs mayprocess only a portion of the received data stream and perform errorhandling, flow control, acknowledgement, and request for retransmissionfor the data it processes. Alternatively, multiple WTs may handle thesame data. For example, redundant transport-layer processing may beperformed by different WTs having uncorrelated WWAN channels in order toreduce errors, and thus, requests for retransmission. In anotherembodiment, only one WT may handle transport-layer processing at anygiven time. For example, a particular WT may be assigned to handletransport-layer processing if it has favorable WWAN-channel conditions.Other criteria, such as load balancing, may be used to select andtransfer transport-layer processing responsibilities between WTs.

In the Network Layer, WTs may perform their own network-layerprocessing, such as addressing and routing. A WT, such as a router, abase station, a switch, or a relay may perform network-layer processes,including managing data congestion, adjusting data frames, packetswitching, and routing. In addition to managing network-layer controlwithin its local group, a network controller may perform network-layerprocesses for the WWAN.

The Data Link layer includes a Media Access Control (MAC) sub-layer andthe Logical Link Control (LLC) sub-layer. Each WT may perform Data-linkprocessing, such as converting received raw data bits into packets andmanaging error detection for other WTs. Similarly, each WT may convertdata packets into raw data bits for one or more other WTs. In oneembodiment, a target WT may perform its own data-link processing.Alternatively, a network controller may perform data-link processing forone or more WTs.

A Physical layer embodiment may provide for performing allphysical-layer processes by a target WT. For example, a target WTdistributes spread, scrambled baseband data to the other WTs, which thenup convert and transmit the target's transmission signal as specified bythe target WT. Similarly, each WT may receive and down convert WWANtransmissions and direct the down-converted signal via the WLAN forprocessing (e.g., descrambling and despreading) by a target WT.

In one embodiment, physical-layer processes may be divided between atarget WT and other WTs in a local group. For example, the target WT mayconvey baseband data and control parameters to other WTs, which thenspread and scramble the baseband data with respect to the controlparameters. Additional control parameters, such as power control, anddata rate control may be specified. Similarly, WTs in a local group maydescramble and despread received data for further processing by a targetWT. WTs may monitor control channels for signals addressed to any of aplurality of WTs in a local group.

In yet another embodiment, a network controller may perform some or allphysical-layer processes corresponding to a target WT. A networkcontroller may perform all physical-layer processes for a target WT (andother WTs in the corresponding local group if it performs higher-layerprocesses for the target WT). Alternatively, some of the higher-layerprocesses may be performed by the network controller and/or other WTs aspart of a distributed computing procedure regardless of how thephysical-layer processes are performed.

Several aspects of physical-layer processing include WWAN-controloperations. Other WWAN-control operations may fall within any of aplurality of the OSI reference model layers. Embodiments andinterpretations of the invention should not be constrained to thelimitations of the OSI reference model. The OSI reference model is ageneralization that may not be suitable for expressing theimplementation of all WWAN-control operations.

In one aspect of the invention, a cellular base station may transmit aprobe signal (e.g., a predetermined signal that is ramped in signalpower) to a plurality of subscriber WTs. A network-management operatorin a local group of WTs may be responsive to the probe signal forindicating a signal power level capable of being received from the basestation. Similarly, the signal power level may be used as an indicatorfor transmit power and/or data rate.

Functions of the network-management operator may be distributed over aplurality of WTs in the local group, and network-managementresponsibilities may be shared by more than one WT and/or dynamicallyassigned to particular WTs. For example, a WT that first detects theprobe signal may be assigned subsequent network-managementresponsibilities, such as predicting forward-link SINR and an associatedachievable data rate, sending an acknowledgement to the base station, orrequesting a particular data rate (e.g., sending a dynamic rate controlsignal to the base station). In another embodiment of the invention,WWAN signals received by a group of WTs may be combined before beingprocessed by a network-management operator.

In one embodiment of the invention, a network-management operator in alocal group performs open loop estimation to adjust reverse link (i.e.,local group) transmit power. Alternatively, closed-loop powercorrections may involve both the network-management operator and thebase station. The network-management operator may send an access probesequence and wait for an acknowledgement from a base station. Initialprobe power is typically determined via power control.

A WT in the local group is typically denoted as being in an inactivestate relative to the WWAN when it is not assigned a forward trafficchannel. However, the network-management operator may assign one or moreWWAN traffic channels to WTs that the WWAN considers inactive. In suchcases, inactive WTs may help transmit and/or receive WWAN communicationsintended for active WTs in the local group. Similarly, active WTs may beassigned additional traffic channels by the network-management operatorfor transmitting and/or receiving WWAN communications intended for otheractive WTs in the group. Such assignments may be invisible to the WWAN,since so-called inactive WTs are used for connecting active WTs to theWWAN. In other embodiments of the invention, complex assignments,including sharing traffic channels between WTs, may be implemented.

A network-management operator may service one or more WTs in avariable-rate state. For example, a forward traffic channel istransmitted at a variable rate determined by the network-managementoperator's data rate control value. The network-management operator maydetermine the maximum data rate using any of a variety of well-knowntechniques. The network-management operator uses a data rate controlchannel to instruct the WWAN what data rate to serve to a particular WTin the local group. In response, the base station selects modulation,channel coding, power and/or number of multiple-access slots.

The network-management operator may direct its instructions to the bestbase station (i.e., the base station having the best channel relative tothe local group) in its active set via addressing (e.g., a coveringcode). Alternatively, the network-management operator may instructmultiple base stations to serve the local group. This may occur when WTscan access more than one WWAN. This may also occur when some WTs arebetter served by one base station or sector while other WTs in the samelocal group are better served by a different base station or sector.

A WT enters a fixed-rate state when its network-management operatorsignals a request for a specific fixed rate from a base station orsector. The WT may transition to a variable rate if it cannot receivepackets at the previously requested fixed rate. A network-managementoperator may select a fixed rate if there is an imbalance (e.g.,different channel conditions) between the forward and reverse links.

In one aspect of the invention, a network-management operator isconfigured to perform connection-layer protocols that are typicallyconducted between a target WT and the base station. For example, thenetwork-management operator may participate in acquisition andinitialization state protocols, air link management protocols,connection state protocols, route updates, and/or idle state protocols.

A WT in an inactive state typically awakes from a sleep stateperiodically to monitor a control channel to receive overhead parametermessages and paging messages. In one aspect of the invention, anetwork-management operator may wait for an activate command from adefault air link management protocol. A network-management operator maymonitor a WWAN control channel for multiple WTs in a local group. In analternative embodiment, WTs in the local group may take turns monitoringthe WWAN control channel. In this case, responsibilities of thenetwork-management operator are transferred between WTs in the localgroup. In another embodiment, a plurality of WTs may monitor the WWANcontrol channel, wherein each WT is configured to monitor the channelfor only a subset of WTs in the local group.

In a network determination state, the network-management operatorselects a channel on which to acquire a base station for a WT in thelocal group. After selecting a channel, the network-management operatorenters a pilot acquisition state in which the network-managementoperator tunes to a particular channel and searches for the strongestpilot signal. Upon acquiring a pilot, the network-management operatorenters a synchronization state. At this point, the network-managementoperator may transfer synchronization responsibilities to the target WT.If the network-management operator (or the target WT) is unable toobtain a pilot, it reverts back to the network determination state.

In the synchronization state, the network-management operator or thetarget WT looks for a sync message on the control channel and sets itsclock to the time specified in the sync message. Failure to receive thesync message or similar failures may result in returning to the networkdetermination state.

The base station undergoes various state transitions in the process ofserving the WTs. In an initialization state, the base station activatesan initialization state protocol, overhead message protocol, and acontrol channel MAC protocol. A network-management operator mayselectively route certain messages through WTs in a local groupcomprising the base station while reserving other messages for WWANtransmission only by the base station.

An idle state occurs after the network is acquired, but before an openconnection is established. The base station initiates an idle stateprotocol, overhead messages protocol, route update protocol, controlchannel MAC protocol, access channel MAC protocol, and forward andreverse channel MAC protocols. In the connected state, base station andthe target WT have an open connection until the connection is closed(i.e., goes to the idle state) or network redirection (goes to theinitialization state). The base station activates a connected stateprotocol, overhead messages protocol, route update, control channel MACprotocol, and forward and reverse channel MAC protocols.

A network-management operator may be configured to direct hand offsbetween WWAN sectors, base stations, and/or networks. In one embodiment,a network-management operator in a local group may measure the SINR oneach pilot in an active set (e.g., a set of base stations that activelyserve the local group) and request data from the sector having thehighest SINR. The network-management operator predicts the SINR for thenext packet and request a higher data rate if it can decode it at thatSINR. The rate request (which may include data rate, format, andmodulation type) is sent by the network-management operator to theappropriate sector using a data rate control channel.

Generally, the network-management operator requests data from only onesector at a time. However, different WTs in a local group serving aparticular target WT may request WWAN channels from multiple sectors ata time on identical or different WWAN channels. The network-managementoperator may coordinate requests for channels from different sectors.Multiple sectors (or base stations) may be configured to serve the sameWWAN channel simultaneously. Alternatively, multiple WWAN channels maybe used to serve one WT in the group. Although the target WT may have abetter connection with a particular base station, the local group as awhole may have a better connection with a different base station. Thus,the network-management operator may dictate that the link be establishedand maintained relative to the group's connection rather than the targetWT's connection.

A base-station scheduler may allocate physical channels for WTs.However, a network-management operator in a local group may providelogical channel assignments to the WTs that are invisible to thephysical channel operation of the WWAN. Multiple WTs in a local groupmay utilize a single WT channel, such as for packet switched datacommunications. Each WT may utilize multiple physical channels, such aswhen higher data rates are required. The network-management operator mayassign logical channels to various physical WWAN channels, and thus,effectively hand off those data channels to other sectors, basestations, or WWAN networks serving those physical WWAN channels.

Data rates requested by WTs may follow a channel fading process, whereinhigher data requests occur when channel conditions are favorable andlower rates are requested as the channel degrades. It is well known thatwhen a base station serves a large number of WTs, that diversity ofmultiple units can mitigate system-wide variations in data rate due tochanging channel conditions. Multi-user diversity teaches that theopportunity for serving good channels increases with the number ofusers, which increases total network throughput.

One embodiment of the invention may provide for a network-managementoperator that dynamically selects one WT in a local group to communicatewith a WWAN at a particular time, even though one or more channels maybe served between the base station and the local group. The selection ofwhich WT in the group communicates with the WWAN may change withchanging channel conditions between the local group and the basestation(s). Thus, the update rate for the dynamic selection may be basedon the rate of change of WWAN channel conditions. This embodiment may beadapted for simultaneous communication by multiple WTs and/or the use ofmultiple base stations and/or WWANs. In another exemplary embodiment,the network-management operator may interleave communications (e.g.,packets) across multiple WWAN channels undergoing uncorrelated channeldistortions. Similarly, a WWAN specifically configured to interact witha local group may interleave messages across multiple WWAN channelstransmitted to the local group. Different WWAN channels may betransmitted and received by one base station or a plurality of basestations. This type of interleaving (at either the local group and thebase station) may be determined by a network-management operator.

In another embodiment, a network-management operator may be configuredto redundantly transmit data symbols over multiple slots or physicalchannels to reduce transmission power or to allocate more power to data.

A network-management operator may employ an authentication protocol toauthenticate traffic between a base station and a MT. For example, anetwork-management operator may identify a particular WT in a localgroup to a base station. The base station may then verify that the WThas a legitimate subscription record with a service provider thatutilizes the WWAN. Upon verification, the base station allows access tothe air interface and the network-management operator (whoseresponsibilities may be transferred to the WT) signs access channelpackets to prove it is the true owner of the session. In one exemplaryembodiment of the invention, the WT and/or the network-managementoperator may use IS-856 Air Interface Authentication.

In one embodiment of the invention, a target WT includes anetwork-management operator that employs other WTs in its local group tointeract with a WWAN. In this case, authentication may be performed onlywith the target WT. In an alternative embodiment, the network-managementoperator resides in at least one other WT, such as a network controller.Thus, authentication may be performed with a network-management operatorin a single terminal that is configured to perform authentication formore than one WT.

A network-management operator may employ a key exchange protocol (e.g.,a Diffie-Hellman algorithm) for exchanging security keys between a WTand a WWAN for authentication and encryption. Typically, there is somepredetermined key exchange algorithm used within a particular WWAN.Public values are exchanged and then messages are exchanged between theWT and the WWAN to indicate that the session keys have been correctlycalculated. The keys may be used by the WT and the WWAN in an encryptionprotocol to encrypt traffic.

In one embodiment of the invention, a network-management operatorresides on a target WT that accesses the WWAN via multiple WTs in alocal group. The network-management operator may be configured toencrypt and decrypt WWAN traffic for the target WT without vitalsecurity information being made available to WTs other than the targetWT. In another embodiment, the network-management operator may reside ina network controller. In this case, the network-management operator maybe configured to engage in security protocols for more than one WT inthe local group. Network-management operators according to variousembodiments of the invention may be configured to participate insecurity protocols used to provide crypto sync, time stamps, and otherelements used in authentication and encryption protocols.

All publications and patent applications mentioned in this specificationare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually incorporated by reference.

Various embodiments of the invention may include variations in systemconfigurations and the order of steps in which methods are provided. Inmany cases, multiple steps and/or multiple components may beconsolidated.

The method and system embodiments described herein merely illustrate theprinciples of the invention. It should be appreciated that those skilledin the art will be able to devise various arrangements, which, althoughnot explicitly described or shown herein, embody the principles of theinvention and are included within its spirit and scope. Furthermore, allexamples and conditional language recited herein are intended to be onlyfor pedagogical purposes to aid the reader in understanding theprinciples of the invention. This disclosure and its associatedreferences are to be construed as being without limitation to suchspecifically recited examples and conditions. Moreover, all statementsherein reciting principles, aspects, and embodiments of the invention,as well as specific examples thereof, are intended to encompass bothstructural and functional equivalents thereof. Additionally, it isintended that such equivalents include both currently known equivalentsas well as equivalents developed in the future, i.e., any elementsdeveloped that perform the same function, regardless of structure.

It should be appreciated by those skilled in the art that the blockdiagrams herein represent conceptual views of illustrative circuitry,algorithms, and functional steps embodying the principles of theinvention. Similarly, it should be appreciated that any flow charts,flow diagrams, signal diagrams, system diagrams, codes, and the likerepresent various processes which may be substantially represented incomputer-readable medium and so executed by a computer or processor,whether or not such computer or processor is explicitly shown.

The functions of the various elements shown in the drawings, includingfunctional blocks labeled as “processors” or “systems,” may be providedthrough the use of dedicated hardware as well as hardware capable ofexecuting software in association with appropriate software. Whenprovided by a processor, the functions may be provided by a singlededicated processor, by a shared processor, or by a plurality ofindividual processors, some of which may be shared. Moreover, explicituse of the term “processor” or “controller” should not be construed torefer exclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, read-only memory (ROM) for storing software, random accessmemory (RAM), and non-volatile storage. Other hardware, conventionaland/or custom, may also be included. Similarly, the function of anycomponent or device described herein may be carried out through theoperation of program logic, through dedicated logic, through theinteraction of program control and dedicated logic, or even manually,the particular technique being selectable by the implementer as morespecifically understood from the context.

Any element expressed herein as a means for performing a specifiedfunction is intended to encompass any way of performing that functionincluding, for example, a combination of circuit elements which performsthat function or software in any form, including, therefore, firmware,micro-code or the like, combined with appropriate circuitry forexecuting that software to perform the function. The invention asdefined herein resides in the fact that the functionalities provided bythe various recited means are combined and brought together in themanner which the operational descriptions call for. Applicant regardsany means which can provide those functionalities as equivalent as thoseshown herein.

The invention claimed is:
 1. A method implemented within a multiuser(MU) multiple antenna system (MAS) comprising: communicatively couplinga central processor to multiple distributed wireless terminals (WTs) viaa network; measuring channel conditions for each of the multipledistributed WTs; selecting a plurality of WTs from the multipledistributed WTs to enhance channel space diversity within the MU-MAS;and transmitting a plurality of data streams concurrently from theplurality of WTs to a plurality of user devices.
 2. The method of claim1, wherein the central processor calculates Multiple Input, MultipleOutput (MIMO) weights from measurements of the channel conditions topre-code the plurality of data streams, wherein the MIMO weights producea plurality of independent MIMO channels.
 3. The method of claim 2,wherein the MIMO weights are calculated for each of a plurality of binsof an invertible transform.
 4. The method of claim 1, wherein selectingcomprises selecting a subset of transmit antennas to enhance channelspace diversity.
 5. The method of claim 1, wherein channel spacediversity is determined from eigenvalue decomposition of a channelcorrelation matrix.
 6. The method of claim 1, wherein the networkcomprises at least one of a wireline network and a wireless network. 7.The method of claim 1, wherein the multiple distributed WTs comprises atleast one of a base transceiver station, an access point, a router, arelay, a repeater, a cellular handset, a wireless modem, and a consumerpremises equipment.
 8. The method of claim 1, further comprisingperforming at least one of user selection and transmit power balancingto enhance channel space diversity.
 9. The method of claim 1, whereinselecting is adapted to at least one of changing user positions,changing WT positions, network loads, throughput requirements,communication services, bandwidth availability, frequency reuse, andchannel conditions.
 10. An apparatus in a multiuser (MU) multipleantenna system (MAS), comprising: a central processor; and alocal-network interface configured to communicatively couple the centralprocessor to multiple distributed wireless terminals (WTs) via anetwork; wherein the central processor is configured to: collect a setof channel measurements indicative of channel conditions between themultiple distributed WTs and a plurality of user devices; select aplurality of WTs from the multiple distributed WTs to enhance channelspace diversity within the MU-MAS; and transmit a plurality of datastreams concurrently from the plurality of WTs to the plurality of userdevices.
 11. The apparatus of claim 10, wherein the central processorprocessing unit calculates Multiple Input, Multiple Output (MIMO)weights from the set of channel measurements for precoding the pluralityof data streams, wherein the MIMO weights provide for a plurality ofindependent MIMO channels.
 12. The apparatus of claim 11, wherein theMIMO weights are calculated for each of a plurality of bins of aninvertible transform.
 13. The apparatus of claim 10, wherein the centralprocessor is configured to select a subset of transmit antennas toenhance channel space diversity.
 14. The apparatus of claim 10, whereinthe channel space diversity is determined from eigenvalue decompositionof a channel correlation matrix.
 15. The apparatus of claim 10, whereinthe network comprises at least one of a wireline network and a wirelessnetwork.
 16. The apparatus of claim 10, wherein the multiple distributedWTs comprises at least one of a base transceiver station, an accesspoint, a router, a relay, a repeater, a cellular handset, a wirelessmodem, and a consumer premises equipment.
 17. The apparatus of claim 10,wherein the central processor is configured to perform at least one ofuser selection and transmit power balancing to enhance channel spacediversity.
 18. The apparatus of claim 10, wherein the central processoradapts selection of the plurality of WTs based on at least one ofchanging user positions, changing WT positions, network loads,throughput requirements, communication services, bandwidth availability,frequency reuse, and channel conditions.
 19. The apparatus of claim 10,wherein the set of channel measurements comprises channel measurementscommunicated from the multiple distributed WTs to the central processor.20. A non-transitory computer-readable medium having computer executableprogram code stored thereon, the computer executable program codeconfigured to: acquire a set of channel measurements indicative ofchannel conditions between multiple distributed Wireless Terminals (WTs)and a plurality of user devices in a multiuser (MU) multiple antennasystem (MAS), wherein the multiple distributed WTs are communicativelycoupled to a central processor via a network; select a plurality of WTsfrom the multiple distributed WTs to enhance channel space diversitywithin the MU-MAS; and transmit a plurality of data streams concurrentlyfrom the plurality of WTs to the plurality of user devices.
 21. Thenon-transitory computer-readable medium of claim 20, wherein thecomputer executable program code is further configured to calculateMultiple Input, Multiple Output (MIMO) weights from the set of channelmeasurements for precoding the plurality of data streams, wherein theMIMO weights provide for a plurality of independent MIMO channels. 22.The non-transitory computer-readable medium of claim 21, wherein theMIMO weights are calculated for each of a plurality of bins of aninvertible transform.
 23. The non-transitory computer-readable medium ofclaim 20, wherein the computer executable program code is furtherconfigured to select a subset of transmit antennas to enhance channelspace diversity.
 24. The non-transitory computer-readable medium ofclaim 20, wherein the channel space diversity is determined fromeigenvalue decomposition of a channel correlation matrix.
 25. Thenon-transitory computer-readable medium of claim 20, wherein the networkcomprises at least one of a wireline network and a wireless network. 26.The non-transitory computer-readable medium of claim 20, wherein themultiple distributed WTs comprises at least one of a base transceiverstation, an access point, a router, a relay, a repeater, a cellularhandset, a wireless modem, and a consumer premises equipment.
 27. Thenon-transitory computer-readable medium of claim 20, wherein thecomputer executable program code is further configured to perform atleast one of user selection and transmit power balancing to enhancechannel space diversity.
 28. The non-transitory computer-readable mediumof claim 20, wherein the computer executable program code is furtherconfigured to adapt selection of the plurality of WTs based on at leastone of changing user positions, changing WT positions, network loads,throughput requirements, communication services, bandwidth availability,frequency reuse, and channel conditions.